I know this issue has been mentioned before, however the troubleshooting procedures I found that were provided by Adobe did not work.
This issue comes when trying to crop a photo. When I select the Crop tool and make adjustments, the adjustments do not show at all except for in the sidebar in the right (I can see the angle change numerically but not physically). Then, after I click done to save the crop, the old image without the crop adjustments is still displayed. The thumbnail of the photo in the collection at the bottom of the "Develop" tab will show the photo with the changes made, but the actual main image does not show the changes.
I have tried uninstalling, signing out, trying a previous version, disabling/enabling GPU, and moving my photos to a different drive. None of these have worked.
I understand this has been an issue for years and yet no fix has been implemented. Every post I find on this issue seems to be years old.
I haven't found any posts in the official feedback forum about crops not displaying properly on a single display. (The feedback forum is where Adobe wants all bugs reported.) Can you post links to the posts you found (in the feedback forum or elsewhere)?
You didn't mention one troubleshooting step, resetting preferences:
I never considered having a second monitor, but I certainly do use one.
Anyway, I took the step of resetting preferences as I had not done that before. That seems to have worked for now... though I'm not 100% sure. My program was operating fine before randomly not working the other day, so I feel like it could come around again soon. Regardless, it seems to be working for now!
Thanks for the help and I'll be sure to update if something else comes up.