I am happy that you have found the problem. But another Z-Wave device shouldn’t actually cause this problem. Your HP23 is probably also affected by the Z-Wave problem “Too much traffic”.
However, this problem was already been significantly improved in the latest experimental firmwares (see changelog). If you haven’t yet installed the latest experimental firmware v10.1.4-rc.3, you may want to give it a try. At your own risk, of course. I have installed this firmware myself and have not noticed any problems so far. I haven’t read any negative feedback about this firmware in the forum either.
