What BEC are you using? The ones built into the esc? ... Might be worth disconnecting your XL (front half of the robot) and seeing if just the rear XXL will drive independent of the front... If it does I'd suggest cutting both BEC links and trying the setup with a fully charged RX pack.... Failing that contact rick maas... He's our local robotpower repair guy, he's re-built and customised the sidewinder in 540 for me and repaired the XXL in 360 for me before at a really good price.