Attempt to upload animated gif image file with size +5Mb gives POST response 504 - Gateway Time-out

Description:

When I try to upload an animated gif file, if it is 5.2Mb the POST fails with error 504 Gateway timeout.

If I try to upload a smaller animated gif, like 2 or 4Mb, the upload goes without issues, in the same way that if I try to upload a 9Mb .jpg image there is also no problem.

It seems that there is a specific problem with +5Mb gif files.

See video (be patient, the video not freezes on (pending) it takes a while to show the timeout):

Storage Type: Filesystem
Maximum File Upload Size (in bytes): 10485760 (10mb)
Nginx configuration client_max_body_size 10mb

Steps to reproduce:

1. Try to upload an animated .gif file with 5.2Mb

Expected behavior:

File sucessfully uploaded:
POST to https://server/api/v1/rooms.upload/ returns 200 - OK

Actual behavior:

Upload fails:
POST to https://server/api/v1/rooms.upload/ returns 504 - Gateway Time-out

Server Setup Information:

• Version of Rocket.Chat Server: 6.5.0
• Operating System: Linux
• Deployment Method: docker
• Number of Running Instances: 1
• DB Replicaset Oplog:
• NodeJS Version:
• MongoDB Version:

Client Setup Information

• Desktop Rocket.Chat Linux 3.9.11(snap) or Browser Version: Chrome Version 120.0.6099.199 (64-bit)
• Operating System: Linux "Ubuntu 22.04.3 LTS" 64bit.

Start by reproducing the rooms.upload POST with an animated GIF around 5.2 MB, then compare it with the reported smaller GIF and 9 MB JPG cases. Review the Docker deployment and Nginx client_max_body_size setting alongside server and proxy logs; done means the GIF upload returns 200 OK rather than 504 under the stated 10 MB limits.