photos crashing on catalina

I had the same problem...it took double the time to download photos from cards...apparently I used my external drive as a back up and it corrupted my Photos...I spent 3 days on the phone with Apple talking to those who work with Photo app...I finally had to buy another external drive and transfer all my photos over to it and then reformat the old one...that seems to have fixed it...but I am a photographer so had so many photos and the Photos app that I used would not open up or took hours to open up...do not use the external drive that you use for everything else with Time Machine to backup your files...use a seperate drive to do this...this is what the Apple techs told me...they also said they had no indication that Catalina did this...but it started when I downloaded Catalina...they said that it made the errors more pronounced and wide spread...