Both
failed on left channel: 25% chances of happening (1/2 x 1/2) if you consider that one channel, L or R, is always going to fail first. So, weird… but not totally unlikely.
The
progressively is interesting as it denotes a very specific failure mode: have you noticed differences between your left and right ears? For example:
> More ear wax on one ear (L), progressively plugging the IEM?
> More sweat on one ear, infiltrating into the IEM, and progressively seizing the IEM driver? Failures due to humidity/sweat are not uncommon…. Especially when using the IEMs for long periods (don’t have time to dry) or, obviously at the gym or for jogging.
> Often wearing one IEM only? I do that quite often when listening into teams meetings on my phone as a cheap “environment aware” mode. This could exacerbates one of the above failure mode or you may “ding” the left IEM more than the right one.
> Wearing the IEMs in bed and sleeping more often on one side vs. the other? May also exacerbate one of the above failure modes, or add a mechanical constraint factor.
> Other things that could be more Left than Right? I don’t think politics is a factor, but who knows: it’s a conspiracy !!!