Installed a new bathroom sink that has one of those spring-loaded drains that you push to close / push to open (not the "usual" external lever and linkages). Obviously this means there is some mechanism within the drain stopper (spring, cam, etc). This is a bathroom sink, so toothpaste, mouthwash, etc, get flushed down this drain, and I suspect the sugars (etc) in those are feeding some sort of biofilm that is forming in the mechanisms, because it's causing a bad odor. I can't figure out how to kill/fix it, though - I've disassembled and used bottle brushes, but it comes back quickly. Did I just get a drain with a terrible design with lots of "captive" space inside for things to grow?