iMovie export fails and disappears

HELP - Trying to Export iMovie and it is failing ever single time.

spent 3 months editing this imovie, starting from scratch would be a nightmare - please help?

My attempts top resolve error:

-copied the imovie library to 3 different computers

• tried exporting to a SSD, USB, USBc, Desktop, Movies folder.
• I deleted the imovie default files
• removed all the songs as a test with just movie
• cleared computer cache
• upgraded Mac OS from sequoia to Tahoe

nothing is helping this to be exported.

Note: iMovie export failed and shows on export location until it finishes and then the export disappears.