Hello,
I've had the EPH-100s for a couple years now and also had issues with the headphones going barely audible in my right ear. Today, I used an eyeglass flat screwdriver to pry off the mesh covering the driver and behind this is a small hole in the center where the sound comes out. There is also a plastic disc with adhesive on it that's between the driver housing and the mesh, and the adhesive holding the mesh and driver together. I'm not sure if it was purely adhesive or a combination of ear wax, but the hole in the center was completely blocked. I removed the blockage with rubbing alcohol and rubbed the adhesive off, and put everything back together. I'm planning on putting some light adhesive on the edges to hold everything together later, but for now the right headphone went from barely audible back to fully functional. Just an FYI for everyone that loves this pair and might be able to try this before they end up throwing out a $100+ pair of headphones that they really like.
Edit #1: I will update this post with some pictures after I have a minute to do so, in the next couple days, per archy121. It is useful to see what we're dealing with.