I've checked the AP_MotorsOcta.cpp, and the motor mixing seems to be Ok, unfortunetly, I can't test it as my V is on repair...and I don't have an APM2 but a APM1
What was your older version you were using ? There was a big change aropund 2.5.4 ...
Have you tried reversing your roll?
My old Version was 2.5.4. I have reverse the Roll Channel but the Gyro works the Wrong way. I can test it later again and tell you.
I can try it with APM 1. Im sure with APM 1 it works. I Flash on my APM 1 the OKTO X und all works fine.
I'd give a go, just to make sure....
I dont know why but no it works. I Erase flash dann i flash Okto V again.. and now all works. Have you makes any Changes in the online firmware?