Why is the sound out of sync in my videos?

Recently the audio is completley out of sync after rendering. Now even the videos I rendered prior to having this problem are out of sync. Other videos that I did not create are fine.

I found out through support, for another issue, that ME is having problems with h.264 format, but I don't under the videos that were already rendered and working fine previously are now being effected.

I've tried watching the videos on my other mac and I'm having the same issue.

I've already reached out to Apple and they couldn't help.

iMac (Retina 4K, 21.5-inch, 2017) 16gb