Pictures corrupting when using remote network drive w. caching in fstab

Description:

When using the mobile Rocket.Chat app on android or the PC app to send one or more pictures to the Rocket.Chat instance, some of the uploaded pictures are corrupted (e.g. one half of the picture is black/transparent). This behaviour could be observed from us on multiple android phones (including three samsung galaxy s10+, a galaxy s20, an older a-series phone, etc) as well as PCs. Also, this does happen to almost every fifth pictures, especially when sending multiple pictures at once (but single pictures were also affected from time to time).

Steps to reproduce:

1. Select one or multiple pictures from the app or from the PC and send them to the server

Expected behavior:

All pictures should be uploaded correctly and with full integrity.

Actual behavior:

Some pictures corrupt as seen in this screenshot:

When clicking on the image with the PC app or using the browser, the following can be observed:

On the android app, the same behaviour is seen. Furthermore, when downloading the file itself to the PC and opening it up with a picture viewer, this mess is shown:

This behaviour could also be observed when sharing pictures directly from the PC app/browser. File uploads on the other hand (for example a .zip-archive) seem to work just fine.

Server Setup Information:

• Version of Rocket.Chat Server: 3.9.3
• Operating System: Debian GNU/Linux 10 (buster)
• Deployment Method: Manual install using this guide: https://docs.rocket.chat/installation/manual-installation/debian/
• Number of Running Instances: 1
• DB Replicaset Oplog: Enabled
• NodeJS Version: v12.20.0
• MongoDB Version: 4.0.21

Client Setup Information

Android app:

• App Version: 4.13.0.22100
• Operating System: Android 10

PC app:

• App Version: 3.0.6
• Operating System: Windows 10 Pro Version 1909

Additional context

The instance does store all uploads (and custom emojis, etc) with the Storage Type FileSystem. The corresponding System Path is pointing to a folder which is mapped to a network drive using the static filesystem fstab. The user rocketchat has rwx permissions on this folder as seen in this picture:

This issue shows the same behaviour as we are getting.

Relevant logs:

Logs from the browser console:

Server logs (after updating to the newest version today):

I20201227-17:21:03.590(1) (migrations.js:120) Migrations: Migrating from version 209 -> 212
I20201227-17:21:03.597(1) (migrations.js:120) Migrations: Running up() on version 210
I20201227-17:21:03.614(1) (migrations.js:120) Migrations: Running up() on version 211
I20201227-17:21:05.022(1) (migrations.js:120) Migrations: Running up() on version 212
I20201227-17:21:05.042(1) (migrations.js:120) Migrations: Finished migrating.
I20201227-17:21:15.046(1) Not migrating, control is locked. Attempt 1/30. Trying again in 10 seconds. 
I20201227-17:21:15.054(1) (migrations.js:120) Migrations: Not migrating, already at version 212
I20201227-17:21:20.478(1) Loaded the Apps Framework and loaded a total of 1 Apps! 
I20201227-17:21:20.685(1) Using FileSystem for custom sounds storage 
I20201227-17:21:20.696(1) Using FileSystem for custom emoji storage 
I20201227-17:21:20.766(1) Updating process.env.MAIL_URL 
I20201227-17:21:23.155(1) ➔ System ➔ startup 
I20201227-17:21:23.156(1) ➔ +--------------------------------------+ 
I20201227-17:21:23.158(1) ➔ |            SERVER RUNNING            | 
I20201227-17:21:23.159(1) ➔ +--------------------------------------+ 
I20201227-17:21:23.160(1) ➔ |                                      | 
I20201227-17:21:23.161(1) ➔ |  Rocket.Chat Version: 3.9.3          | 
I20201227-17:21:23.162(1) ➔ |       NodeJS Version: 12.20.0 - x64  | 
I20201227-17:21:23.163(1) ➔ |      MongoDB Version: 4.0.21         | 
I20201227-17:21:23.164(1) ➔ |       MongoDB Engine: mmapv1         | 
I20201227-17:21:23.165(1) ➔ |             Platform: linux          | 
I20201227-17:21:23.167(1) ➔ |         Process Port: 3000           | 
I20201227-17:21:23.168(1) ➔ |             Site URL:                | 
I20201227-17:21:23.168(1) ➔ |     ReplicaSet OpLog: Enabled        | 
I20201227-17:21:23.169(1) ➔ |          Commit Hash: e47dc05618     | 
I20201227-17:21:23.170(1) ➔ |        Commit Branch: HEAD           | 
I20201227-17:21:23.172(1) ➔ |                                      | 
I20201227-17:21:23.172(1) ➔ +--------------------------------------+ ```

Start by reproducing image uploads through the FileSystem storage configured on the network-mounted fstab path, comparing them with ordinary file uploads. Done means uploads from the Android app and PC app remain intact and match the original images.