Wanted to share what did and did not work for me.
First noticed the problem about a week ago, but I don't make a lot of outgoing calls with the OBI, so I'm not sure when it started.
Based on threads on Google forums I think something changed on the GV side because people are reporting the same problem with non-OBI hardware devices.
I have two OBI200, here's what I did on each:
Device #1
* Was on 5757EX
* Upgraded to 5898EX
- no improvement
* Hardware reset ; reconnected to OBI portal ; reconnected to Google Voice
- problem fixed
Device #2
* Was on 5757EX
* Via OBI portal deleted service provider ; reconnected to Google Voice
- no improvement
* Upgraded to 5898EX
- no improvement
* Hardware reset ; reconnected to OBI portal ; reconnected to Google Voice
- problem fixed
The one obvious sequence I didn't try was to start with a hardware reset and resetup GV without upgrading firmware.
I remember that I had a tweak in the settings to fix some earlier problem with GV from a year or two ago. If everybody else with this problem also had that tweak then maybe GV changed so that the tweak now breaks things. The hardware reset then removed the tweak. Sorry, don't remember what it was.