I haven't been on this thread for a looong time but hear my story about defective Monk+ and succesful Monk+ surgery.
Long time ago I bought two pairs of red edition Monk+ and second pair had channel imbalance problem, that right side didn't have as much bass and it was slightly quieter also. I didn't think much of it back then because it's 5$ earbud, it's okay to have occasional bad units. I did blast it with high volumes and lots of bass and it did help a bit but didn't make right channel identical with left. Time passed on and those faulty monks was forgotten. Sometimes I still used them while for something talk related stuff, as for music they didn't work out at all. But now after long time I tried faulty monks again and channel problem had somehow gotten even worse. Now right channel was dramatically more quiet and didn't have much bass at all. So tonight I ripped right faulty bud open and took driver element entirely out from shell. I just stated that driver -seems- to be okay, and then I just put it back together. I didn't really waited for it, but now sound was completely cured of right channel and it now sounds identical with left channel. So it seems like the driver element was somehow "stuck" with shell and it couldn't move properly, hence producing thin and quiet sound. But for you to know, this wasn't actually first time I met this kind of problem, as my Hifiman RE400 did have such problem when I bought them NEW, which I also fixed myself.
But now my glorious handsome beautiful red Monk+ are on prime of their life. SOUNDS GOOOD!