Exporting Keynote Movie slide

Hello. Have been creating ‘movie’ posts for Instagram using Keynote for some time. Just recently, it has started to bonk out right after trying to export a new slide. (See pic below)

Note: (Enlarged) Background image / movie export settings have always been the same and it has worked well. The only piece that changes each time is the headline.

I have tried to export other slides in the presentation, and have also created a new / similar document and even attempted to place the slide in another file and export it, but each I continue to get the same non-save. It just cuts out. Have also cleaned out my iCloud so there should be plenty of storage available. All my other exports (photos) seems to still work.

Thank you / any thoughts appreciated.

Always wor