Rendering video hangs in photoshop 21.2.1

I have created a short (21 sec.) video in photoshop based on a tutorial.  The video contains stills and movies.  When I try to render it the CPU utilisation shoots up on one processor and then nothing seems to happen.  I have tried leaving it for up to 10 minutes with no result. I have created a similar project in Premiere using the same clips and effects and it renders in about 1.5 minutes.

The program becomes unresponsive and I have to kill the process to close it.