That is a strange one. Could be the famous chinese quality control. I see you're in Arizona so maybe your air filter is letting dust in there. If it's an older carb then maybe time to replace?
I have a brand new nt speed carb with a very sticky slide that I can only move by pushing with a chopstick. I can't figure out how to hone the slide chamber without wearing down the guide pin. I don't want to sand down the slide itself. I'm going to try the dremel with the plastic brush wheel. That's all I can think of.
good luck