With file naming set up to move and rename, Picard silently deleted the source files even though the target directory was not writable to the current user.  This is not exactly friendly, even though the fix is to make sure target directories are writable.  However, in a very large collection that has move around over time from different source computers, there can be occasional directories with incorrect permission.

If the target is unwritable, don't say the operation completed successfully by setting the green check mark.