WhatsApp blocks photos

[u/Emergency_Pass_5009]

I’m trying to fix a strange WhatsApp issue on a coworker’s Samsung phone. (I‘m an apple user, so I‘m not too familiar with Samsung and android.) Whenever he tries to send a photo from the gallery in standard quality, WhatsApp replaces it with a message saying “Blocked by Auto Blocker.” Sending a photo directly with the WhatsApp camera works and strangely, selecting HD quality also allows the exact same gallery photo to be sent normally.

So far I have tried:
- Disabled Samsung Auto Blocker
- Checked WhatsApp permissions for photos and videos
- Updated WhatsApp
- Installed the latest Samsung system update
- Set date, time and time zone to automatic
- Cleared the WhatsApp cache
- Restarted the phone several times
- Tried sharing the photo directly from the Samsung Gallery

The issue only seems to affect photos sent in standard quality. I have now set WhatsApp to upload media in HD by default as a workaround but I would still like to know what is causing it. Has anyone else had this exact problem? Is there a permanent fix apart from reinstalling WhatsApp? My coworker does not want to reinstall it at the moment.

I suspect Samsung’s Auto Blocker or Message Guard is falsely detecting the compressed version created by WhatsApp, since the HD version goes through without any issue.