I have been using Obihai for ~7 yrs. now, first the 110, then the 200 for the last couple years, with Google Voice.
I have also set up these devices for numerous folks, also for use exclusively w/GV.
I have had virtually no problems that were not user error, firmware update, or product failure related.
That has dramatically changed since sometime in the spring: the most persistent problem now is that incoming calls are lost after the 3rd or 4th ring.
This happens with two other people whose Obihai 200 I setup.
I have checked all possible settings on the Obitalk dashboard & w/GV: no problems there.
The clearest indication that the problem is w/Obihai firmware: if I dial the other Obihai 200 devices directly (using **9) the same problem presents with 4 to 5 rings, and I then get my own voicemail (not the voicemail of the person I am calling).
Current firmware is 3.2.2.5898