[Focus Merge not working after update to 1.9.0.932]

Please advise how to get Affinity Photo working again:

I updated Affinity Photo to 1.9.0.932 yesterday. Since then the Focus Merge has not been working correctly.

Over the last month or so I have been shooting pictures of the moon and using Affintiy Photo's Focus Merge as a form of "Luck Imaging". I have actually been getting some very good results (example: https://www.flickr.com/photos/apfrsscf/50889011527/).

Since the update, the Focus Merge has hung when I tried to stack 150 frames. I previously was able to stack up to about 200 frames successfully. But this time it hung so badly that I could not even get Control-Alt-Delete to come up. I had to lean on the power switch in order to force the computer to shut down.

So then I tried stacking just 10 frames. It went through the algorithm ok, but only rendered a completely black image without the subject.

Thank you for your assistance.