Burned neutral wire on breaker
Most likely, the neutral wire connection failed because the wire was not properly torqued down.  Even experienced electricians cannot set a torque any more reliably then their spouses - that's been tested.  It's why Code now requires use of torque screwdrivers.
The connection got hot, passing heat down the circuit neutral (copper is a very good thermal conductor), enough to cause thermal damage to adjacent wires.  Note the damage to the neutral pigtail.
So, this failure does not condemn the GFCI breaker.  It certainly does not disparage the other GFCI breakers.
Switching breakers will fix it, because you'll be unscrewing and re-screwing the screws, changing the torque setting. You'll probably be luckier this time.
Unfortunately the breaker that had the burnt-up wire is toast.  The heat was at the wire-breaker contact point, and if it was hot enough for heat to walk down the copper wire and burn other wires, it was also hot enough to ruin the breaker plastics, gut the GFCI electronics, or throw the thermal bi-metal strip out of calibration.  Into the trash it goes.