I had that very same problem - mine kept popping out in the neck position. I don't know if you tried this adjustment or not, but I'll post it so anyone else with this issue can try it.
The Switchcraft toggle switch can be problematic that way (I don't know what they use on SEs), but you may not need to replace it. Jack Gretz told me how to fix it, and he was right.
If you open up the control cavity, and operate the switch, you will see that the toggle has four steel spring plates with very small contacts attached to the inside of each plate. A "bat" that is on the other side of the toggle that you actually operate moves the springs apart, or lets them all connect. So in the middle position, all the contacts touch. When you move the toggle, the "bat" pushes one of the springs and its associated contacts away from the inner contact plate that's nearest it. This allows only one or the other pickup to make contact.
Obviously, these springs have to be manufactured to close tolerances to make that happen, and they can get very easily worked out of shape.
At the end of each outer spring is a little protrusion in the metal of the spring (it reminds me of the tail fins of an airplane) that's bent from the metal of the spring at an angle. If the angle of this bend isn't in adjustment, it can't grab the "bat" correctly, and the switch won't stay in the right position.
This little protruding bent tail part can be bent very slightly upwards (by that I mean, upwards when the guitar is lying with its back open on the bench so the control cavity is facing you) with a needle nose pliers; and I mean slight changes are the way to go, kind of a bend it just a titch, see if it holds, try again, etc., until you get it to stay in position. You don't want to overdo it.
Obviously sometimes the switches need to be replaced anyway. PRS sells the parts, and that's who I'd use to source it.