I had the same sorts of issue with the SE215's as noted above. Sound would cut out in the left ear periodically and/or when wiggling the cable.
I detached the left cable and discovered that there was substance which appears to be a very thin oil on the male portion (cable end). I disconnected the right one too and found the same substance on the connector. The coating was actually so thin that the only way I could tell it was there was to run the tip of a finger along the metal and then look for a reflective patch. I used a q-tip to wipe down both connectors before attaching the wires again and having a listen. So far I'm almost 40 hours of use later with no dropped audio.
If It crops up I'll post here, but removing the "oil" from them cleared mine right up.