Some attachments preview not shown

Description:

Some PNGs (and maybe some another formats ... IDK) are not displayed as image (preview, can show it as an image in client, etc.) but another PNGs are displayed as image with preview, view in client, etc.

Steps to reproduce:

1. Send image (mainly tested with PNG)

Expected behavior:

Image is sent and shown in client with preview and option to view and download

Actual behavior:

Some images are displayed clearly but another images are shown just as file to download. No preview, no view window, etc.

Server Setup Information:

• Version of Rocket.Chat Server: 3.12.2
• Operating System: Debian 10 (server)
• Deployment Method: tar
• Number of Running Instances: 1 to 3
• DB Replicaset Oplog: ? (can't understand)
• NodeJS Version: v12.18.4
• MongoDB Version: 3.6.21

Client Setup Information

• Desktop App or Browser Version: (latest, auto updated in many devices)
• Operating System: any (🍎 / 🐧 / android / ...)

Additional context

Relevant logs:

The report identifies no files, tests, or entry points. Start by reproducing the behavior with PNG attachments on the reported server and client setup, then compare an image that previews with one that is treated only as a downloadable file. Done means the affected image formats consistently show a preview and can be viewed and downloaded.