Adding CC to Slide Video, freezes when generating thumbnail images

I'm working in Captivate 2019 and have created many projects with slide videos and the closed captions are added and work just fine. However, this time around Every. Single. Time I try to add CC it freezes (stops responding) when I click "ok" and it is generating the thumbnail images. I have to force quit to do anything and then of course the captions aren't there when I open it back up because I had to force quit. Has anyone expereinced this and found a solution? My next idea is to add CC to the videos directly but then users can't turn them off, so that isn't an ideal solution, but it is a last resort.

Thank you!