Its a machine not a human it would always be mobile unless it gets its tracks blown off or the engine overheats which would require a lot of fancy engine pushing driving.
Its the principle behind it, but I bet a fat person would have adjusted better than a machine. A fat person will be used to the weight and his legs would be stronger than a skinny person.
Actually, the Tiger II used the exact same engine as the Panther. It just weighed 25 tons more!
Same engine but more weight? Thats extra strain put on the engine plus the fact you are trying to drive it like a medium tank.