Joining the convo late here, but I had this problem at the beginning of last season. I have a 6" riser on mine and figured it loosed from the extra leverage I was exerting onto the steering shaft. With this in mind I didn't want it to happen again, so I pulled the engine and built a cross member of sorts that supports the side of the mount closer to the engine. It bolts on the end of the steering shaft bushing and bolts to the aluminum panel on either side of the steering shaft. This is to help support side to side pressure exerted from me trying to carve on the sled.
These guys are all right, OEM type rivets!! This is a long job, but not particularly hard. I have heard of insurance companies totaling out sleds when these center exchangers get destroyed just because of the time involved on replacing them....not to be a debbie downer, just to give you a realistic view of what your bill could be, going to the dealer.
I was in a hurry when I put that support in and I don't think I have a picture.