Haven't had an issue with driver failures, the cable does have a very flimsy mmcx connection. One IEM may be more loose on one side than the other but you just have to press into the connection from the IEM to get a better seal, I do that and I never have problems with audio cutting out.
But if the mmcx port is too weak, Sennheiser will almost always just ship you a new pair if you send it to them.
The IEMs themselves are built excellently and connect just fine. And they sound phenomenal, definitely worth having to deal with fiddly cables every now and again.