Epson brand lamps vs non-Epson lamps

Is your projector doing something odd after replacing the lamp with a cheaper lamp that claims to be compatible? We've been taking numerous calls and seeing projectors in our shop for service that give misleading errors but have a common thread: a cheap non-Epson lamp. Sometimes it will appear to be an overheating condition. Other symptoms might lead one to suspect a faulty ballast unit. But when we find a knock- off lamp in the unit, that's where we start and frequently finish our troubleshooting.