This reply will be non-specific, as I'm only a pilot. We're operating a VEMD AS350B2, and changed the VEMD black box after approximately a year in service. I don't remember what initiated the black box replacement, but we had a couple of dubious issues prior to that-
A hot-start indication with a very competent pilot. The pilot was new to VEMD, doubted that he'd over-temped but medical crew claimed to have observed an exceedence. Inspections showed no damage.
A very, very competent, conservative and diligent pilot had a rotor overspeed alert on shutdown. This, too, was inspected and no damage discovered. The overspeed was 1 RPM above power applied limit. The circumstances made this report seem exceedingly improbable.
Our VEMD black box had water damage caused by the nose vent. We've since had no alerts. One display issue, somewhat related in that the pilot opened the vent inflight after a period of heavy rain, which resulted in an in-cabin shower and a blanking of the VEMD. The nose-vent drain tube was kinked. The vent sits over the VEMD black box, more or less, and the drain issues expose it wetness.