Do you have a pleco nemesis?

Blue Panaque Pleco - Baryancistrus beggini L239 is mine. I have had >100 plecos in 20+ tanks for many years. I think I've had or have almost every available pleco except a few of the smaller ones (I like them >5"). I've tried L239 several times without luck. None of them have lasted > 6 months. I don't have any trouble growing mangos L47 or GN L177 etc. but L239s just waste away. I'm not looking for advice on how to grow L239 because I'm pretty sure I could by treating it like a princes with special food (I have too may plecos I like better that are easier to take care of). I'm interested if there is a pleco that just doesn't work in your tank(s) with your normal husbandry. This could be useful for people not familiar with plecos to help them avoid some of the more sensitive ones.