Question that obviously shouldn't happen but while it's bolted in if torqued down to spec would the cup still pre load the mount and essentially not affect function. If that's case it is very possible every mount is failing on install or right away and just no one realizes except extreme diy guys that pull it out again shortly after.
I torqued mine down to spec. I believe the reason why the passenger side fails is because the mount not only sees the weight of the engine , but it is also under a rotational force from the torque of the engine. This force pushes down on the passenger side mount while the driver side is being pulled up. This is the reason only the passenger side mount is upgraded in the 335is model and not both mounts.
My car started to have a nasty vibration when coming to a stop, also lots of noise under part throttle. I had just installed new turbos so I thought they had possibly failed. I pulled my down pipes to check on the turbos, which were fine. That’s when I found the broken mount. I backed the 6 bolts out on the subframe without completely removing them, the subframe could then drop down a few inches. I unbolted and slide the mounts out. Luckily my garbage man hadn’t picked up my can yet, I fished the old stock mounts out of the trash and threw them back in.
I should have listened to people about the 034 mounts!!!