Thank you @lock042 - after I posted this I saw a post where you recommended someone go back to Siril 1.22, which I’ve done. I uninstalled 1.2.4 and downloaded and installed 1.22, and it all seemed to go well. Unfortunately the program froze on the first of the last four pp_light_###.fit files it was processing 
- I’m assuming now that I have to start over…? Is that correct?
Thanks again!