error 1609629695

the error i get:

Export Error
Error compiling movie.

Render Error

Render returned error.

Writing with exporter: H.264
Writing to file: /Users/(my user)/Downloads/pls.mp4
Writing file type: H264
Around timecode: 00:00:21:18 - 00:00:21:25
Rendering at offset: 21.067 seconds
Component: H.264 of type Exporter
Selector: 9
Error code: -1609629695

This is with after effects.

I have tried setting to Mercury Playback Engine Software Only. I have cleared my media caches. I have deleted all the effects and transitions on the clip on the timecoded error area. I have deleted the whole clip itself at that time. I have tried exporting to desktop to downloads to various folders etc...

Really wish this error didn't exist because I get it almost every time I try to export with transitions.