Tested today with TrackIR5 and I can confirm this bug. When using TrackIR 5 the hotbar keys barely work. They may work after smashing the button for like 10-20 times but it's unplayable.

The issue is fixed when you either disable TrackIR from the settings or move the TrackClipPro away from the TrackIR receiver's "view" (making it go unactive)

Tested on: TrackIR 5+TrackClipPro, Windows 8.1, i7-3820, GTX670
DayZ version: 0.44.123802