Beware of the knee jerk reactions to a problem. Obviously there is a brake problem. If you have the ability (or get a mechanic), check over the brake system and find where your problems are. But don't spend money on a complete new brake system, that's just silly. As many have already said, it's probably a seized caliper or something on the wheel that was hot. This can happen when a vehicle sits for long periods (and sometimes not just then).
But don't replace the whole system. By that logic you should replace the whole motorhome (better safe than sorry, right?)