I know this problem. Some times it appears also on my system. I do not really know why this error occurs. I belive it is a Windows background service (windowssearch?) which detects that the source folder has changed and tries to update his database. This locks access to the file and LR can not remove it.
Sorry, but I do not have a solution for this problem.
Well that's a long workaround, when I can just move the last file quickly in LR.
But thanks for the idea.
THG_BO, I disabled Windows Search service and have been working with LR for the last couple of hours. I've moved around 5 or 6 batches of images and so far have had 100% success. So that may be the solution.
Workaround #2: my workflow does not depend on or need moving photos from here to there, you could do this too, and it would take less time than what you are doing
This bug has been around since at least LR 2 and was acknowledged by Adobe several years ago. Please add your vote and your possible workaround to this thread in the official feedback forum:
That thread reports that the problem was narrowed down to Windows, but I don't believe anyone had previously tied it to the Windows Search service.