diff --git a/android/app/src/main/AndroidManifest.xml b/android/app/src/main/AndroidManifest.xml
index 81772ab..1afb1d6 100644
--- a/android/app/src/main/AndroidManifest.xml
+++ b/android/app/src/main/AndroidManifest.xml
@@ -13,6 +13,7 @@
             android:theme="@style/LaunchTheme"
             android:configChanges="orientation|keyboardHidden|keyboard|screenSize|smallestScreenSize|locale|layoutDirection|fontScale|screenLayout|density|uiMode"
             android:hardwareAccelerated="true"
+            android:enableOnBackInvokedCallback="true"
             android:windowSoftInputMode="adjustResize">
             <!-- Specifies an Android theme to apply to this Activity as soon as
                  the Android process has started. This theme is visible to the user
diff --git a/lib/models/app.dart b/lib/models/app.dart
index 71f6c3f..18f4bf5 100644
--- a/lib/models/app.dart
+++ b/lib/models/app.dart
@@ -75,6 +75,17 @@ class App extends BaseApp with DataModelMixin<App> {
     final notifier =
         adapter.ref.read(installationProgressProvider(id!).notifier);
 
+    if (canUpdate) {
+      final match = await packageCertificateMatches();
+      if (match == false) {
+        notifier.state = ErrorInstallProgress(
+          Exception('APK certificate mismatch'),
+          info: 'Update is not possible',
+        );
+      }
+      return;
+    }
+
     final installPermission = await Permission.requestInstallPackages.status;
     if (!installPermission.isGranted) {
       final newStatus = await Permission.requestInstallPackages.request();
@@ -101,8 +112,8 @@ class App extends BaseApp with DataModelMixin<App> {
         notifier.state = ErrorInstallProgress(Exception(e));
         return;
       }
-      notifier.state = RequestInstallProgress();
 
+      notifier.state = RequestInstallProgress();
       final result = await InstallPlugin.install(file.path);
 
       if (result['isSuccess']) {
@@ -110,7 +121,7 @@ class App extends BaseApp with DataModelMixin<App> {
         await adapter.ref.localApps.localAppAdapter
             .refreshUpdateStatus(appId: identifier);
       } else {
-        const msg = 'Android installation failed';
+        const msg = 'App has not been installed';
         notifier.state = ErrorInstallProgress(
           Exception(msg),
           info: result['errorMessage'],
@@ -162,13 +173,15 @@ class App extends BaseApp with DataModelMixin<App> {
   }
 
   Future<bool?> packageCertificateMatches() async {
+    if (latestMetadata!.apkSignatureHash == null) return null;
+
     final flags = PackageInfoFlags(
       {PMFlag.getPermissions, PMFlag.getSigningCertificates},
     );
 
     final i = await packageManager.getPackageInfo(
-        packageName: id!.toString(), flags: flags);
-    if (i == null || latestMetadata!.apkSignatureHash == null) {
+        packageName: identifier, flags: flags);
+    if (i == null) {
       return null;
     }
     final bytes = i.signingInfo!.signingCertificateHistory!.first;
@@ -425,6 +438,10 @@ class ErrorInstallProgress extends AppInstallProgress {
   ErrorInstallProgress(this.e, {this.info});
 }
 
+extension ExceptionExt on Exception {
+  String get message => (this as dynamic).message ?? toString();
+}
+
 final installationProgressProvider =
     StateProvider.family<AppInstallProgress, Object>(
         (_, arg) => IdleInstallProgress());
diff --git a/lib/screens/app_detail_screen.dart b/lib/screens/app_detail_screen.dart
index 80b227f..ac04db2 100644
--- a/lib/screens/app_detail_screen.dart
+++ b/lib/screens/app_detail_screen.dart
@@ -231,18 +231,6 @@ class AppDetailScreen extends HookConsumerWidget {
                                                   .apkSignatureHash!));
                                           context.showInfo(
                                               'Copied APK certificate SHA-256 to the clipboard');
-                                          app
-                                              .packageCertificateMatches()
-                                              .then((match) {
-                                            if (match != null && !match) {
-                                              context.showError(
-                                                title:
-                                                    'APK certificate mismatch!',
-                                                description:
-                                                    'Please let us know',
-                                              );
-                                            }
-                                          });
                                         },
                                         child: Row(
                                           mainAxisSize: MainAxisSize.min,
diff --git a/lib/utils/extensions.dart b/lib/utils/extensions.dart
index 986298b..0438256 100644
--- a/lib/utils/extensions.dart
+++ b/lib/utils/extensions.dart
@@ -58,7 +58,7 @@ extension StringWidget on String {
     });
   }
 
-  String substringMin(int size) {
+  String substringMax(int size) {
     return substring(0, min(length, 80));
   }
 }
diff --git a/lib/widgets/app_drawer.dart b/lib/widgets/app_drawer.dart
index 6d3271e..a6ef6fa 100644
--- a/lib/widgets/app_drawer.dart
+++ b/lib/widgets/app_drawer.dart
@@ -84,7 +84,7 @@ class LoginContainer extends HookConsumerWidget {
                       }).catchError((e, stack) {
                         context.showError(
                             title: e.message ?? e.toString(),
-                            description: stack?.toString().substringMin(200));
+                            description: stack?.toString().substringMax(200));
                       });
                     },
                     builder: (context, child, callback, buttonState) {
diff --git a/lib/widgets/drawer_container.dart b/lib/widgets/drawer_container.dart
index 5cb5615..d3372eb 100644
--- a/lib/widgets/drawer_container.dart
+++ b/lib/widgets/drawer_container.dart
@@ -1,8 +1,6 @@
 import 'package:flutter/material.dart';
 import 'package:hooks_riverpod/hooks_riverpod.dart';
 import 'package:zapstore/main.dart';
-import 'package:zapstore/main.data.dart';
-import 'package:zapstore/models/app.dart';
 import 'package:zapstore/utils/system_info.dart';
 import 'package:zapstore/widgets/app_drawer.dart';
 
diff --git a/lib/widgets/error_container.dart b/lib/widgets/error_container.dart
index 95125c5..5f7c43b 100644
--- a/lib/widgets/error_container.dart
+++ b/lib/widgets/error_container.dart
@@ -49,7 +49,7 @@ class ErrorContainer extends HookConsumerWidget {
           ),
           Gap(6),
           Text(
-            stack?.toString().substringMin(80) ?? '',
+            stack?.toString().substringMax(80) ?? '',
             style: TextStyle(
               fontSize: 12,
               color: Colors.grey,
diff --git a/lib/widgets/install_button.dart b/lib/widgets/install_button.dart
index d6395b8..31fd396 100644
--- a/lib/widgets/install_button.dart
+++ b/lib/widgets/install_button.dart
@@ -54,8 +54,7 @@ class InstallButton extends ConsumerWidget {
               },
             ErrorInstallProgress(:final e, :final info) => () {
                 // show error and reset state to idle
-                context.showError(
-                    title: (e as dynamic).message, description: info);
+                context.showError(title: e.message, description: info);
                 ref.read(installationProgressProvider(app.id!).notifier).state =
                     IdleInstallProgress();
               },
@@ -109,7 +108,13 @@ class InstallButton extends ConsumerWidget {
               VerifyingHashProgress() => Text('Verifying file integrity'),
               RequestInstallProgress() =>
                 Text('Requesting ${app.canUpdate ? 'update' : 'installation'}'),
-              ErrorInstallProgress() => Text('Error, tap to see message'),
+              ErrorInstallProgress(:final e) => Padding(
+                  padding: const EdgeInsets.only(left: 8, right: 8),
+                  child: Text(
+                    '${e.message.substringMax(64)} (tap for more)',
+                    textAlign: TextAlign.center,
+                  ),
+                ),
             }
         },
       ),
@@ -187,7 +192,7 @@ class InstallAlertDialog extends ConsumerWidget {
             child: user != null
                 ? Text('Install', style: TextStyle(fontWeight: FontWeight.bold))
                 : Text(
-                    'I trust the signer, install anyway',
+                    'I trust the signer, install the app',
                     textAlign: TextAlign.right,
                   ),
           ),
diff --git a/lib/widgets/wot_container.dart b/lib/widgets/wot_container.dart
index a49b11d..4a68673 100644
--- a/lib/widgets/wot_container.dart
+++ b/lib/widgets/wot_container.dart
@@ -29,6 +29,10 @@ class WebOfTrustContainer extends HookConsumerWidget {
                 trustedUsers.firstWhereOrNull((u) => u.npub == npub) != null;
             final trustedUsersWithoutUser =
                 trustedUsers.where((u) => u.npub != npub).toList();
+            if (trustedUsersWithoutUser.isEmpty) {
+              return Text(
+                  'No trusted users. This may be a service error and you may want to try again later.');
+            }
             return RichText(
               text: TextSpan(
                 children: [