Suppose you are using a bath tube chassis?
If yes, I assume that there are two possible explanations for your problem:
1. The Mamba is certainly far too much for drifting. Usually 15T brushed (or equivalent brushless) is the max...
2. The excess power together with the "soft" bath tub (even with the carbon reinforced lightweight bath tub) would most probably lead to the drivetrain 'bending' the chassis slightly so that the belts get enough play to turn upside down...exspecially when drifting and the motor is revving at very high rpms.
Rgds,
Andy