Writing Changes into XMP is slow

Not sure how Mac handles it, but on my windows environment, I do huge batches of metadata edits. Because of the sluggish behavior of Lightroom, I have resolved to work on my image storage with several computers simultaneously. That means that the XMP and changes have to be written into the files to not get conflicting versions. Unfortunately, Lightroom gives little to no info on the progress in saving the metadata (currently looking at 324 images having their metadata - xmp - saved. 12 minutes going on forever and still not finished). Be it because Lightroom crashes or I have to restart due to deadline approaching ( a word Adobe does not seem to understand), I frequently have to restart the app, and just as often do I discover that parts of the files that I worked on did not get their metadata updated as instructed. This in spite of Lightroom assuring that the metadata will not be lost but saved later. I have asked Adobe numerous times for a solution, as this drives me nuts. I do not know what is worse; to have the app crashing and having to start again, or to have to restart the app and then start the detective work of finding out which images got the metadata written and which images did not. It is maddening, and it has been going on for years (at least 2011, on different computers) without Adobe providing a solution, workaround or suggestion of what causes it. Last session with support suggested read/write privileges being reset to read-only somehow. but we still don't know why.  

Found a suggestion in another thread which seems to have fixed this issue for me. 

1. Disable writing metadata to xmp temporarily.
2. Filter entire catalog on "metadata status" and look for anything not "up to date".
3. Resolve your conflicts and retry wrting the metadata.
4. Re-enable writing to xmp
5. That allowed me to close Lightroom without it hanging on the xml writing.

I had "changed on disk", "conflict detected" and "unknown".  The "conflict detected" message is baffling to me as I don't know what other app could possibly have touched these files.  All of them were years old and I hadn't touched them in a long time.  I to "overwrite settings" although I frankly have no idea exactly what that did.  I had no edits that I recalled or cared about on those images.  There were no XMP's in the folders so there were apparently no previous edits.

The "changed on disk" error seems to have been partially due to read-only files.  Other surrounding files in the effected folders were not read only and I don't know how a few files got that way.  I also don't understand why the native image file being read only impaired Lightroom from writing data to XMP files.

The "unknown" set were all .mov video files.  Lightroom offered no option to fix these.  They have been in the catalog for years over multiple version updates without issue.  I took no action on them.

Same issue and same setup.  Immediately after the last Lightroom update I got the same message about updating XMP and assumed it was due to the update so allowed it to run . . . an run  . . . and run.  After 24 hours it still hadn't finished so I quit.  Next exit of LR did the same thing but eventually XMP updates finished and LR exited.  Now several days and several reboots and app start/shutdown cycles later, I'm getting a similar message with only an option to "Stop".  The most recent Lightroom session included an upload of ~100 images and only edits on one.  This is absurd.   Clearly Adobe instroduced a bug in the last "update". 

Yup, same issue here after upgrading to LR Classic v13. Ryzen 9 3900x RTX3080 32GB RAM, 2 TB NVMe SSD

Have you updated to the latest release of LrC 13.0.1?