swoop, #4 cables would be small but when you get into the */0 (ought) the cable diameter increases the larger the first number, so 4 /0 would be rather large, like for a fast charger, normally a battery would have 1/0 or 2/0, with 2/0 being the larger of those 2 cable sizes.
I would normally say this is most likely caused by the cable charger half laying on the floor and getting run over, causing the lack of spring pressure because the plastic part that hold pressure is weakened (but not all the way broken)and when it gets hot during charging, it then weakens the same part in the truck half. spreading the problem further.