Sporadic functioning is a sign of a loose/broken connection.

I think I recall someone stating that the VX units are somehow sealed (encased/coated) to prevent water damage and therefore more complex to repair.

I did a lot of research online on these things and don't remember where I found that information.

I also recall Trooper (and some other) units are very similar, but may have different programming. Never could determine for sure if they were the same or if they could be reprogrammed.