I've never heard of anyone suffering any issues whatsoever with the older models bud. They were, and continue to be, 100% bombproof.
That surprises me as I've never heard anyone mention any problems with Microns (where as if you ask 3 or 4 owners of newer Delks you'll find someone that's suffered). I still have a set of the original Microns, in fact I used to carry one around with me as a spare for when my Delks went wrong. Twenty years old, changed the battery once in that time, never let me down. It's what convinced me to go back to Fox which turned out, for me, to be an excellent move.