A battery that is not charged sufficiently and sustaining a charge while under a load will cause intermittant issues without codes. Load test the battery for bad cells. Low voltage will reak havoc. So make sure the battery is good and fully charged before further diagnostics.

the motors have speed sensors in the bearings and they need to be replaced. very common problem. the three "inmotion" controllers are interchangeable so if you want to verify the diagnosis you can rotate them and see if the problem follows the controllers. when you get done waisting time testing, pull the motors and replace the bearings