I saw this happen on an F-150 V8 with the same basic type air filter and housing.
Take a look at the air filter. I have seen the black plastic cap on the end of the filter come off and get sucked into engine side of the intake a filter housing. Chokes the air flow basically killing the engine. When the engine dies , so does suction and the plastic falls down. Then you go again and the process repeats, depending how long it takes for the plastic to get sucked back into the tube.
You would think the shop would have looked at the air filter, but you never know…
2018 E450 Forester 2291s