Reply to Traktor X1 MIDI layer doesn't work

So every six months or so I post this problem here or on the native-instruments board; I still can't believe I'm the only one in the world this happens to. My X1 works perfectly in normal mode, but MIDI mode (shift+hotcute, the hotcue light turns green) fails to work at all. The X1 is sending MIDI signals, but Traktor refuses to acknowledge them. If I reinstall the X1 software (which I do every so often) this is temporarily fixed, but then it seemingly randomly goes out again - not sure if it's when I move the X1 to a different port on the USB hub or what. Reimporting the tsi for my X1 midi layer doesn't help at all; the only solution is to reinstall the X1 software and controller manager again.

Does nobody else have this happen? Do most people not use the MIDI layer at all?

BTW Mac OS X, Traktor 2.1.1, but this has been happening at least as far back as 1.2.something when I got the X1. Thanks!