My IE-900 -- replaced about a year ago -- is still okay.
But the $20 eBay cable (which I replaced the stock OEM Senn cable with; the stock de-laminated after only a year), went bad at the 3.5mm connector. I had the new/never-used OEM Senn cable, still in the box, so I went for that ... and after a few hours, the left ch. began cutting out. VERY hard to pinpoint as i suspected it might be my amp cable or DAP cable. It drove me nuts pinpointing the exact source because the issue occurred so randomly.
Anyway, I gently removed the connector and applied a tiny amt of Deoxit. (as i did when I orig. installed it a few hours earlier). And the issue went away for day, and then came back full force.
Very weird that my aftermarket cable went kaput, and now the brand new OEM cable. Maybe it wasn't the new OEM cable? It's brand new, after all and Senn's own, factory new.
PHOTO: Senn on left; aftermarket on right. Notice washer on Senn.
One thing I have noted is that the aftermarket cable -- even for a cheap $20 Chinese ebay unit --seems to insert a bit deeper with more tightness and confidence. None of the two OEM Senn cables I have used feel confident, and they allow the chassis to rotate way too freely.
Anyway, a Google search points to a possible answer/and diy solution. It's in the Reddit post by another IE-600 owner. Same cutout issue.
I have not done the OEM washer mod (Reddit) nor have I replaced / repaired the aftermarket. I assume the washer -- not sure it was ever used in my orig 2021 Senn OEM cable -- is the cause of cutouts. Last time I reinserted, I use a little more gentle force to compress it. Seem to be ok. Stay tuned. But - after last year -- I will never trust Sennheiser. Never purchased another Senn product since 2021. And regret the uber $ ie-900 purchase more than ever. So many other IEMs now, way cheaper and more reliable. And with superior 2-pin connectors to boot.
Pathetic that Sennheiser still has connector issues. Since the 1970s ... and well into the HD-600 age. And now with IE - x00.