i think i figured out the problem by experimenting around a bit trying to replicate the circumcisions
after the same thing occurred when i downloaded grimm3x7
here are what appear to be the necessary ingredients:
-add a half dozen or more torrents all at once
-use magnet links rather than torrent files
-click the links when the system is low on memory because of other applications
-choose the option to have an add torrent dialog box that allows changes in title or location
-there should be a lag as you wait for the add torrent boxes to open
-after a delay, when all the boxes open almost at once, click ok in quick succession to add them all as
fast as possible
it seems that this can activate the torrent download before the metadata is dowloaded which includes
the file extension. i declare this mystery solved. 🙂