I'll leave the resuming there for now.
Yes the behavior has changed. Synchronization was completely re-factored in 3.8 beta. As part of that, order of actions has changed. Previously the deletion was done after transfers, not before. However it still must have failed, because the deletion of filepart file was still scheduled. But the file no longer exists once the transfer finishes, so the deletion must have failed.
I'll try to solve it in the next release.
Thanks. I will look forward to your next release.