What is the white mold on mushroom block? What is the white stuff in the mycelium? Maybe it's stroma

What is the white mold on mushroom block? This white stuff could be a stroma. It occurs between the substrate and the film in the block at the end of incubation. Oyster mushroom mycelium forms from its hyphae a protection of the substrate from high temperature and low humidity.
00:20 Stroma - white mycelial tissue between the film and the substrate
00:50 Yellow spots on the substrate
01:19 Overheating of the block during incubation
02:00 white stuff in the block slot
03:10 recovery of mycelium between the first and second flush