[Tyler2517]

I would be that your frame is either to ridged and all 4 wheels are not getting the same amount of traction, or your weigh is not distributed correctly leaving uneven traction.

Depending on how your algorithms (i am not a programmer all i know is that we wright our own C++ code for it) work can you manually compensate (ie try turning when you rotate). Or implement PID on each of the wheels we have has success with both methods and depending on the driver we have enabled our PID or disabled it.