After LR Classic 13.0 and update 13.0.1 Lightroom is behaving weird on my second monitor.
Before I could use the compare mode on the second monitor when in the develop module on the first without any issues.
Could zoom in and out on the comparisons.
After the update this behaves odd.
Sometimes it will zoom in and out as before but most of the time it doesn't and one of the selected pics for comparison won't even show (just black) or sometimes even zooms in at a different percentage compared to the other. This only occurs when in the Develop module.
Switching from Compare to Loupe on the second monitor sometimes won't work either - display goes black.
When I switch to the Library module on the first screen there's no issue.
I've got a very robust Windows system with 32 GB of RAM and a NVIDIA GeForce RTX 3060 Ti 8GB of RAM which before (v 12.5) just did the job without any trouble.
Seems like Adobe rushed to do this update but forgot to test it thouroughly.