Dear Thomas,
I’m using an older KNX router (version 1.0) from MDT and always had trouble with it using the TUNNEL mode. So even under OH 2.x, I’ve only used it in ROUTER mode. You can see my configuration in this post:
openHAB 3.0 –> KNX. Don’t have channels, Post #24
But even with ROUTER mode and this specific Router, I still had troubles concerning *-control items. My experiences I also have described here:
KNX control item doesn’t respond to read request from the bus