Hi ! Funny, I did exactly the same observation this week end : I also did a rainy trip with my 650 on my handlebar and I had also an heratic behaviour : very difficult to "clic" on an icon, self changing pages... To be confirmed on a deeper test.
Since I have this device (~1 month now) I'm quite happy with it, a lot of good points. I had until now an Edge 705 but I changed for a bigger screen an a more powerfull processor (moving a map was very slow with the Edge)
Like many guys, I did a track compare with these two devices on my handlebar and I'm a little bit desapointed about Oregon accuracy : not better than my old Edge, often worse. I was expecting something more accurate with Waas/Egnos integration but no progress on this side for me (v3.10). Linked to this, my GPX track file is not as "clean" as it was with my Edge. I tried several settings (recording auto, based on time, based on distance) but I did'nt found a way to have a clean and accurate track.
Nothing important, I still happy with this device.