The bigger the radius of the wheels, the greater the moment inertia. The greater the moment inertia, the harder it is to move, but once it starts moving, the harder it is to stop. Like rolling and stopping a boulder vs a marble. Takes a lot more more force or torque.
Didn’t see this thread back in my but keep your tires inflated pretty hard to reduce rolling resistance
This thread is pretty old, but I came across a similar issue, but on street wheels.
Here’s my thread about it: http://www.electric-skateboard.builders/t/space-cell-pro4-maximum-charge-stuck-at-94/10269/4
Don’t know what could’ve happened. I rarely take the battery/case off.