I have a Solix 15 G2 and 12 G2 and have gone through each update. Am currently running 3.970 and I would just go ahead and go to that update rather than updating to an older version.

The one thing to be aware of is that Humminbird is having so many Bluetooth issues that they are limiting you to a single device type Bluetooth connection on each control head. I think this started with 3.900. Depending on your boat setup and what kind of Bluetooth accessories you have, this could be a limiting factor for you.