The el cheapo ESC's from Ebay (the Blue's), have a limited reverse, like 50%, and also do have a brake bias depending change of direction.

Those combined with small differences in timing (even center timed) on the equaly inexpensive motors used in batterydrills will give an noticable inbalance in drive.

One of the reasons some of the machines use a gyro, and the main reason why team RCC prefers RW specific controlers like the Scorpion XXL mk1 or IBF 4.X

Those can be trimmed, adjusted and pampered to an extend even modern RX/TX sets can't do with single drive ESC's ,even with extensive reprogramming.