Mac OS12.1 Intel

Trying to do holy grail TL's and the transitions aren't sticking meaning I go through the process, keyframes in LR and after the visual previews render out the changes in exposure are still there, visually. They seem to be changed in the spreadsheet. Back in LR when I export them for the outputs they don't have the smooth change like they should, it looks like waves where it gets brighter then darker then brighter, etc. I can post the video to vimeo if that would help.

Went back to 5.8 and it is working fine.

I find it unlikely that that's an issue in the beta. Make sure to have set the correct Masks Version in the LRTimelapse settings according to your Lightroom Version. Remove the sequence from Lightroom, then restart the editing via "Metadata / Initialize".