My guess is that the piston in reservoir was set up with too small a space for the gas. So when the shock got hot and fully compressed to the bump stop gas pressure skyrocketed due to the high compression ratio of a small gas space and something had to give.
Ask the shop guy to what height he set the gas piston. If you get a "huh" kinda look well, you have your answer.
FYI, I set the piston about 10 mm in from the wet side, the cylinder is mostly gas-filled. And I check the final installed height with a probe through the vent port before buttoning everything up final.
"Hells AL is right."Zuber "Bad roads, good people. Good roads, bad people." Mama Espinoza
“Ride first, tart second. Sorry bro but that’s the way it has to be.” Cbrit, 2008
“You gas it where I brake!” trackday passenger, Thunderhill, 2005 "Especially since he's one of the fastest riders on the planet, on any surface!" Earwig, 2014