I lost 2 skimmers recently, more specifically the pumps. One was in the strip fire/burn, I'm unsure why the pump no longer works, everything seems fine but who knows, maybe it's an electrical short that did it in. The other was a smaller sedra pump (2500? I'm guessing btw), and apparently the impeller magnet bulged outward, so the pump is useless unless I buy another impeller (one thing you should try, sometimes its not calcium magnets do pop outward).
My current medium price skimmer is an ASM g3, and I'm having issues with this too, the pump itself is fine, but for some -unknown to me- reason the summabooger keeps overflowing, I have a gate valve on it as well, dial it back so bubbles are really low, and even then something happens over night, and the skimmer overflows then goes back to regular levels, like something caused it to go whacky.. who knows maybe I'm getting spawning events every night. So I really don't know what the hell is causing it, or how to fix it at this point.
But one tank is skimmerless until I can find a replacement pump, at this point I'll probably do any ol' powerhead with a venturi valve, although I would like to reuse the needle wheel impeller it has, but it is my softie tank so it probably will be ok for a while. And the other tank might as well be skimmerless because the sucker keeps overflowing, and any gunk that does built up in the cup will end up spilling back into the tank.
Or they get comprised and rust inside out. With Sedras it's usually calcium though.