“Pressurized air spray” infact does not exist. They are liquefied gases, like propane-butane (flammable), or otherindustrial gases. When the come out from the can, they cool down, and can take with the water from the air, or cause injuriesof the CMOS (by freezing it). Be careful.
This case has been solved by a longer normal cleaning with alcohol, under the microscope.