CORE-11377, I ran into multiple issues related to renaming a directory, and then moving a subdirectory back to the original location.
updatedir.c which reproduces this issue, creates two directories, each with a testfile:
First it renames c:\movetest\1 into c:\movetest\2.
Next it moves c:\movetest\2\u back to c:\movetest\1.
The main problem is a data corruption after doing this. I'll add more details below.