I have tried all the tips I can find, but no luck finding a clue on a subtle problem.My 3DR 2013 Y6B, recently upgraded to 4S batteries from 3S, went through the calibrations including ESC, still tends to drift backwards and to the left. CofG seems OK. Was trying to do an auto tune but either the weather or this issue prevented it. So I changed the Log Bitmask to 786430, checked for Vibes and any irregularities. GPS Number of Sats and HDOP OK throughout. I am attaching logs if anyone is inclined to have a look.
In the past I successfully flew this with a Tarot 2D gimbal and GoPro and had good stability and handling.
Thanks in advance for any help.