So, after backwards and forwards with WhatsApp about the video sending bug (affecting those who have updated to Android 12 and OneUI 4.0) they have finally acknowledged the bug and said they are working on a fix for a future update. At first they denied knowing anything about it and told me to send them a video of what happened so I tried to explain that's the problem, I can't as it'll be unviewable (I have both issues - some have a green line, some are just scrambled - I've have instances of both). So to illustrate what I meant I sent them a video - it was scrambled (you have to use WhatsApp to chat to their support). We had further back and forth resulting in them telling me to restart my phone to fix it... 🙄. Eventually I tried to explain it wasn't just me and sent screenshots (with all the names blanked out) from this forum and the Playstore listing with people reporting the same problem. Finally got a message back yesterday "We're aware of the issue and are working on fixing it in a future update of WhatsApp.". So fingers crossed it won't take long.
I too have been in contact with WhatsApp who had the cheek to assume that my problem (green lines) was caused because I had not updated WhatsApp or cleared the cache or data. How wrong they were. They have also told me that they will look into my problem.