I apologize for doubting your tech. Moisture could certainly damage unsealed tuners.This guitar was in a flood, and sat for some time, so I had to lubricate them just to get them to function again.
Just one of the tuners seems to stick when tuning down.
The tech is good, so I don't think he's off base here.
(Gotoh has good reviews, but I don't seem to see a matching replacement from them.)