For what it's worth, I am running the same hardware version and same firmware load that you cite and have never experienced either problem you describe. I've been using this device before and after the google changes and only had one small problem because I wasn't allowing Obi to update my device automatically. I'm a comcast customer and formerly used an Asus Router with Merlin Firmware, but recently upgraded to a netgear orbi, which is working well.
You're in a tough spot because OBI support is essentially non-existent. You've bought a device, from which they derive no further revenue and for which they have zero incentive to help you with, so you have to make a decision about how much Free is costing you.
Try subscribing your SP2 -4 to another service like Flow route and spend a small amount of money to test their services. If stable, you can choose whether or not it makes sense to port your number away from Google. If not stable, I'd be looking into your network connection.
My 2 cents.
Tom