And the white pigtail is on the neutral bar?
If so, the first thing I'd try is changing the breaker. If it still trips, then I check the conductors between the breaker & the lugs of the unit. If they all check fine, then the problem is in the spa.
I'd leave it at that and have the spa company called out. Once my wires hit the lugs, that's as far as I go. I don't repair spas.
In winter, why do we try to keep the house as warm as it was in summer when we complained about the heat?