for one, shure's 846 are a new iem, there might just not be enough people who A own them, or B changed the connectors.
the mmcx is proven to cause a great deal of issue, i would look towards the se535 and the ue900 to get a better idea of a more used and circulated iem than the 846.
the mmxc connect can get dirty, it can be come loose after time from change to different cables, this looseness can lead to shorts, dirt in the connect can also lead to shorts in the signal, the ring in the connector can become worn and this can allow for a great deal of movement of the iem housing thus causing shorts... this is ALL from expierence with this connector.....ALSO when you put the male side of the pin into the female side, the female side has a ridge, when you first connect the connectors you heard a nice firm snap, to let you know you have made a good connection....over time the female groove wears out and the snap is no longer a snap but more like a click, this too can lead to shorts in the sound.
I love the pin design i feel like although there have been cases where people broke pins off in the housing this could be from carelessness or just man handling the iem and cable. im not saying its perfect. however the mmxc has alot more to fail than the pins to. pin design is very simple, there not alot to wear. and it doesnt wear like the mmxc does.
thats just my expierence and my opinion.