Error message when attempting a Shape Blur in PS CC

I keep getting this message when attempting to blur a small layer in a TIF file:

Could not complete the Shape Blur command because of a program error.

I've got the most recent PS version 21.0.1

Catalina 10.15.1  on a Mac Pro 'trash can'

32 GB RAM, 150 GB of available disk space.

The file is big (650 MB), but smaller than many similar I edit sucessfully all the time.

There are several layers and the one I want to blur is a very small 'patch' I copy/pasted

This has been going on for a week or two.

To fix it I have tried:

A restart, then shutdown and restart

reset PRAM

uninstalled non-current PS and Bridge versions

uninstalled PS 21.0.1 and restarted

and finally reinstalled PS 21.0.1

None of it worked.

Any ideas?