diff --git a/app/javascript/new_design/dossiers/auto-upload-controller.js b/app/javascript/new_design/dossiers/auto-upload-controller.js
index a2780a65e..84e5f594b 100644
--- a/app/javascript/new_design/dossiers/auto-upload-controller.js
+++ b/app/javascript/new_design/dossiers/auto-upload-controller.js
@@ -1,6 +1,9 @@
 import Uploader from '../../shared/activestorage/uploader';
 import { show, hide, toggle } from '@utils';
-import { FAILURE_CONNECTIVITY } from '../../shared/activestorage/file-upload-error';
+import {
+  ERROR_CODE_READ,
+  FAILURE_CONNECTIVITY
+} from '../../shared/activestorage/file-upload-error';
 
 // Given a file input in a champ with a selected file, upload a file,
 // then attach it to the dossier.
@@ -68,6 +71,12 @@ export default class AutoUploadController {
         description: 'Vérifiez votre connexion à Internet, puis ré-essayez.',
         retry: true
       };
+    } else if (error.code == ERROR_CODE_READ) {
+      return {
+        title: 'Nous n’arrivons pas à lire ce fichier sur votre appareil.',
+        description: 'Essayez à nouveau, ou sélectionnez un autre fichier.',
+        retry: false
+      };
     } else {
       return {
         title: 'Le fichier n’a pas pu être envoyé.',
diff --git a/app/javascript/new_design/dossiers/auto-uploads-controllers.js b/app/javascript/new_design/dossiers/auto-uploads-controllers.js
index 18b0bc882..a469f115f 100644
--- a/app/javascript/new_design/dossiers/auto-uploads-controllers.js
+++ b/app/javascript/new_design/dossiers/auto-uploads-controllers.js
@@ -1,12 +1,9 @@
 import Rails from '@rails/ujs';
 import AutoUploadController from './auto-upload-controller.js';
-import { fire } from '@utils';
-import { FAILURE_CONNECTIVITY } from '../../shared/activestorage/file-upload-error';
-
-//
-// DEBUG
-//
-const originalImpl = FileReader.prototype.addEventListener;
+import {
+  FAILURE_CLIENT,
+  ERROR_CODE_READ
+} from '../../shared/activestorage/file-upload-error';
 
 // Manage multiple concurrent uploads.
 //
@@ -24,10 +21,11 @@ export default class AutoUploadsControllers {
     try {
       let controller = new AutoUploadController(input, file);
       await controller.start();
-    } catch (error) {
-      // Report errors to Sentry (except connectivity issues)
-      if (error.failureReason != FAILURE_CONNECTIVITY) {
-        throw error;
+    } catch (err) {
+      // Report unexpected client errors to Sentry.
+      // (But ignore usual client errors, or errors we can monitor better on the server side.)
+      if (err.failureReason == FAILURE_CLIENT && err.code != ERROR_CODE_READ) {
+        throw err;
       }
     } finally {
       this._decrementInFlightUploads(form);
@@ -42,25 +40,6 @@ export default class AutoUploadsControllers {
         .querySelectorAll('button[type=submit]')
         .forEach((submitButton) => Rails.disableElement(submitButton));
     }
-
-    //
-    // DEBUG: hook into FileReader onload event
-    //
-    if (FileReader.prototype.addEventListener === originalImpl) {
-      FileReader.prototype.addEventListener = function () {
-        // When DirectUploads attempts to add an event listener for "error",
-        // also insert a custom event listener of our that will report errors to Sentry.
-        if (arguments[0] == 'error') {
-          let handler = (event) => {
-            let message = `FileReader ${event.target.error.name}: ${event.target.error.message}`;
-            fire(document, 'sentry:capture-exception', new Error(message));
-          };
-          originalImpl.apply(this, ['error', handler]);
-        }
-        // Add the originally requested event listener
-        return originalImpl.apply(this, arguments);
-      };
-    }
   }
 
   _decrementInFlightUploads(form) {
@@ -73,12 +52,5 @@ export default class AutoUploadsControllers {
         .querySelectorAll('button[type=submit]')
         .forEach((submitButton) => Rails.enableElement(submitButton));
     }
-
-    //
-    // DEBUG: remove the FileReader hook we set before.
-    //
-    if (this.inFlightUploadsCount == 0) {
-      FileReader.prototype.addEventListener = originalImpl;
-    }
   }
 }