Windows 10, fully up to date, LR Classic fully up to date. PC too old to update to Win 11. Where attempted subject selection fails - because LR cannot find a subject - the program 'sticks'. The rotating arrow replacing the 'Done' button at bottom right is apt to keep right on rotating - and on and on. Other editing of the photo is still partially possible but in particular framing cannot be adjusted and when making another selection such as brush the overlay does not appear, nor do edits of the selection. Close this photo, go to another, most editing appears possible - including subject selection - but attempt to adjust framing and the former photo appears. The only way to fix the bug is to quit the program (no need to back-up) and restart.
I have tried purging Camera Raw cache and increased its size. No telling yet wehether this helps!
Please post your System Information as Lightroom Classic (LrC) reports it. In LrC click on Help, then System Info, then Copy. Paste that information into a reply. Please present all information from first line down to and including Plug-in Info. Info after Plug-in info can be cut as that is just so much dead space to us non-Techs.
Lightroom Classic version: 11.2 [ 202201281441-a5b5f472 ] License: Creative Cloud Language setting: en Operating system: Windows 10 - Home Premium Edition Version: 10.0.19044 Application architecture: x64 System architecture: x64 Logical processor count: 4 Processor speed: 3.3GHz SqLite Version: 3.36.0 Built-in memory: 16267.2 MB Real memory available to Lightroom: 16267.2 MB Real memory used by Lightroom: 1725.9 MB (10.6%) Virtual memory used by Lightroom: 1845.6 MB GDI objects count: 682 USER objects count: 2103 Process handles count: 3437 Memory cache size: 69.2MB Internal Camera Raw version: 14.2 [ 1028 ] Maximum thread count used by Camera Raw: 3 Camera Raw SIMD optimization: SSE2,AVX,AVX2 Camera Raw virtual memory: 223MB / 8133MB (2%) Camera Raw real memory: 224MB / 16267MB (1%) System DPI setting: 96 DPI Desktop composition enabled: Yes Displays: 1) 1920x1080 Input types: Multitouch: No, Integrated touch: No, Integrated pen: No, External touch: No, External pen: No, Keyboard: No
As you are not running 4K and beyond, and as your GPU is fairly old, not only might you not get any benefit from turning on the preferences option to use Graphics Processor, you might get issues. Typically a problem NVIDIA 800 Series and older. Not sure if the Auto Sky or Subject mask needs that option on.
so GPU driver v456.71, latest is v472.98. The Auto Sky mask (not sure about the subject mask) has caused issues around old GPU and Video drivers, more of an issue with integrated video controls (think Intel) as opposed to descreate graphic controls. But you may want to update that driver, recommend custom install option as to cause a clean install.
Ah-HA! I think I have it. The bug seems to strike only - or mainly - when I have Photoshop running alongside Lightroom - so presumably a resource issue on my slightly elderly and modestly sepcified PC. Yes, I have now run some comparisons - with PS running the Lightroom subject mask 'process' doesn't complete.