Flying indoors? You must be kidding. My wife, and Bud (the cat), would never allow that. The flights were just my normal flying I do around here. GPS-ATTI and no VPS.
I get the sense that it can't be fixed. That's why I was looking for a way to reduce, at least temporarily, the symptoms. It looks like @FunN4lo has had some success with this.
Sorry about the indoor remark. I forgot that not everyone has a gymnasium in their backyard (including me). I think you are right about there not being a permanent or reliable fix. Maybe that's why they added the C2+Gimbal wheel adjustment ability. Oh well.