After cropping photos they become blurred and not clear ,help

Since I put from Mojave to Catalina my photo after editing enlarge on full view blurred. I am working as I always did, and my photo quality is good enough to make big enlargements. What an I doing wrong ?

I am not cropping with a 3rd editor, and my pixel dimensions are as high as I can get, and the results are exhibition quality. The only system I use now, for the last three years, is the Photo app on this Apple PC. This problem did not appear till I changed from Mojave to Catalan.

What are the pixel dimension before and after cropping?

Are you cropping with Photos or a 3rd party editor?

What system and Photos versions are you running?

Similar problem same questions to be answered.