Problem with file extension missing when saving from Photoshop cc2019

Photoshop cc2019

I'm experiencing an issue when saving photoshop files - ie the file extension doesn't get added. In fact, sometimes it simply saves as a .psd file, regardless of file type jpeg, tiff, etc, then wont open unless I manually correct the file extension. I've checked 'always apply file extension' in preferences / file handlng. I've re-installed fromm CC.

Any clues?

btw I've recently upgraded to Mac OSX Catalina.