The same issue that was annoying me on KPE now it's happening on my Oxygen :/. The ear moisture building up onto the nozzle filter and slowly blocking the sound decreasing the sound pressure level so you perceive a channel imbalance.
Pics of the filter after ~1hour of usage:
On KPE it was wayy worse the channel imbalance and slower to dry the filter out, but now on O2 leaving it 1 minute it's enough to the sweat dry out and back to normal but after weeks I felt the filter needed to be replaced since I was needing to get higher volumes (70/100) compared to my first week (50/100) to get the superb sound. Hopefully, Tanchjim provides a lot of extra filters (I think even KXXS now comes with some extra filters too since it's a constant issue on KPE) but it seems not the best fix for this annoying issue.
I've noticed this happens more often when I use black firmer silicon tips, might those tips elevate the temperature in my ears causing this? I think full metallic IEMs aren't for me, lol.