I noticed that there are files left over if the source file is deleted before the first complete transfer.
PC A adds file test, transfer to PC B starts, on PC B a file called “~syncthing~test.tmp” is created. If during initial transfer the Original on PC A is deleted, the tmp file on PC B stays there. I would expect that the tmp file is being deleted.
Tested with 0.11.6 on both Windows and Linux.