Photos problems since Catalina 10.15.5 update

Anyone else having problems with their Photos app since updating? As a keen DSLR photographer I'm pretty familiar with using Photos and editing, but after the update - boom! It's all gone belly up!

Firstly, I've always been able to drag and drop onto my desk top directly from photos (I've heard that this is an anomaly and most other people have to 'export' them to their desktop). Since the update however, only some photos will drag and drop - others when i try to do so I get the spinning wheel of death until eventually i have to force quit due to lack of activity.

Another issue is during the editing process - photos appear blurry until I click the edit button at which time they crisp up ready for editing. It's almost like they don't load properly until I hit the edit button. Then when I've finished editing and click 'done' I move onto the next photo - ( or I may go back to a previous photo sometimes to re-edit something) and for some reason it won't give be access to the 'adjust' option. I can see the adjust button there at the top of the window, but it's not clickable. Weird.

And then finally another problem is when I try to upload the photos to facebook or other webpage directly from said webpage - only some of the photos that I've just imported into my photo library are simply not in there! So I close the webpage, go back into photos, and yes - of course they are there right where I left them. So instead I have to drag and drop them onto the desktop in order to upload them.....aaaand the cycle starts all over again.

I have done the 'Photo Repair' and this has not helped at all.

Another thing that bears mentioning just in case it has some relevance - is that when I open my Photos it now opens on the same photo every time I open it (a random pic from the last import). It does not open at the end of the photo library like it used to - well it used to actually open at the beginning of the photo library for a split second while it loaded, and then drop straight to the bottom - i.e. the last photos I imported.

What gives? Can anyone help? TIA : )