I have not noticed that so far, but I will pay attention. For power I am using a 7.4 Volt 2500 Lipo, with a 15c discharge rate.
But you can have 2 different issues the servos themselves, poorly made or cheap servos do not always get to the same point every time.
If it is power, you should be able to isolate it by raising your bot, removing all but 1 leg, actually remove the servos from the board. Run a few cycles and see where you end up. If all is good keep adding legs back, until things start going off, at that point isolate just that leg.
If it all works ok in isolation then you have a power issue.
It is a pain in the but though.