The tower is very weak as we all know and this allows the play to pull it half way out of gear and "split" the cases.
The best thing to do is brace the shifter assembly to the engine so it moves as one piece. I have spoken with Scott at XMF, Funco, etc and the consensus is that bracing works great. At one time there was a cable system available but it was overpriced compared to the bracing and it brought other adjustment issues to the table. Here is how mine was done. Pretty easy and cheap. The flat bar bolting to the belt inspection cover simply bolts to a tab that is welded on the passenger side of the shifter assembly. You can build it in about 30 min and it works great. Wish I had a better pic but hope this helps.