Nautilus cut/paste stops working and a subsequent "move" moves files into nirvana

Similar to bug https://bugs.launchpad.net/ubuntu/+source/nautilus/+bug/1322925 I've found today that Nautilus again suddenly stops allowing you to do cut/copy/paste - drop-down menu greyed out - while keyboard shortcuts (at least CTRL-X) keep working, as it seems. And it has gone more severe, as I *lost files* when I tricked it into moving files.

In window #1 I had two tabs open, where I selected a number of files in the left tab. Suddenly the cut and paste shortcut stopped working. Next I went into the drop-down to see if that's still possible - nope - greyed out.
But then, out of laziness, as I didn't want to restart Nautilus, just opened a new window (#2) with the destination folder. I then went back into source window #1to press the "cut" shortcut again: CTRL-X - without visual feedback on file icons of files being select for cut. I didn't care about this quirk, switched into the newer window #2 to paste and the files in window #1 disappeared but never arrived (!) in window #2 - Nautilus had moved the files somewhere, probably into nirvana. Nothing important lost for me, but potentially very dangerous. Using Ubuntu since version 4 Warty, I've never lost files like that.
If Nautilus, on moves, does a copy first, and then deletes the source, it seems it thought the copy completed (which failed) and then unlinked the files in source.

Nautilus 3.10.1 on Ubuntu 14.04