Like Swoop said it depends what mode of travel you have selected and would help if you can share more details of the problem, im assuming this is a steering issue snd not a drive issue.

Im also pretty sure since this is an ET unit its an electric truck using linear steer sensors encorporated inside the LF and Rear steer cylinders not prox switchs but I could be wrong. Check your stop bolts on the Rear and Front left wheels.

When in forward mode make sure the LF wheel is perfectly parrallel with the front leg and the tire is not toed in at all.

When in side mode make sure the rear wheel is perfectly parrallel with the back of the truck.

Any deviation will cause the sensor to not read correctly and give you mode change and steering issues, most likley cause would be the stop bolt has come loose not allowing said wheels to go to the fully locked positions.

Since your having an issue with the front I would segguest having a good look at the rear tire in particular.

If stop bolts are in adjustment and the wheels are sitting in the correct positions you may have a calibration issue and will need curtis software.

Low battery or battery issues can cause steer sensors to read incorrectly as well.