Diagonal lines on cross-dissolve transition

Hello Adobe Community,

I have not seen anything yet about diagonal lines on a transition (versus a whole clip).  Please see screenshot at the bottom of this post.

What has not worked:

• I deleted the transition and replaced it with a new one;
• copied the sequence into a new sequence;
• restarted Premiere Pro

The only thing that works is shortening the length until it is out of the problematic (diagonal-lined) area, but I would like to keep the transition lengths consistent.  Any ideas as to why this little area is causing problems?  Note: the purple clip is a video clip (.mp4).

This error resulted in failed export (even though it had rendered to green).  Error message also posted below.

I have PremierePro 24.2.1 and OS Sonoma 14.4.  MacBook Pro Apple M2 Max