I thought the silver colored protective wrap that’s on the MLVSS looked a bit minimal, so I put heat shrink over it. This caused the MLVSS to stop working. After investigating I discovered that the side of the silver colored protective wrap that’s against the MLVSS circuit board conducts electricity. It’s a sufficiently good conductor for my multimeter to beep for a short circuit when I press the test leads against the wrap. I’m guessing the heat shrink pressed the silver wrap onto the board and caused a short circuit somewhere. Fortunately after removing the heat shrink and the factory silver wrap the board now works.
The FLVSS has wrap that’s black on the outside, but the inside towards the circuit board is the same silver, and my multimeter registers a short circuit on that too, when the test leads are pressed against it. On the FLVSS at least there is a piece of cardboard between the circuit board and the conductive wrap. However the cardboard on my FLVSS isn’t big enough to cover the whole board, so there would still be a risk of a short circuit.
I’m removing the factory wrap from these boards and just using my own insulating shrink wrap. I’ll tape the factory wrap on top of the heat sink to retain the pinout information.