This issue shows up in a published service plugin but it can also be duplicated somewhat in a normal collection. The same error messages print in a normal collection when reordering images.
Issue: LR Classic v11.2 rearranging images in "Custom Order" causes errors
LR Classic: v11.2, Build [202201281441-a5b5f472]
OS: Windows 10 Pro, v21H2, Build 19044.1526
Step 1: Create published collection which contains some images
Step 2: Publish images to service
Step 3: Change sort order to "Custom Order"
Step 4: Drag an image to a new location
Expected Result: No errors
Actual Result: 120 error messages print to debug console and LR is unstable for a bit, sometimes publish service is non-responsive for up to 5 minutes. Sometimes it recovers and sometimes I have to restart LR.
BTW, I tried two previous times to post this where I cut and pasted the error messages as part of the post body and both times my post was marked as spam... So, I've attached a screenshot of the first few of the 220 error messages