The reason this happens is the bumper that the red stub rests against deforms under pressure changing the angle of the retaining bumper wall which then allows the red stub to pop over. Instead of being a 90° wall it relaxes to say an 88° wall when the plastic between the two ends lifts up off the ski top.
The solution is two-fold. First, deepen the corner of the bumper so that the effective angle of the bumper wall exceeds 90° to hold it down better. If you don’t have a dremmel, a good round file should do the same thing and probably provide a better margin of safety so that you don’t accidentally remove too much material. I used a ¼” diameter grinding stone in the dremmel which ground the plastic slow enough to yield good control.
Second, after the corner of the bumper is deeper, glue the entire black plastic piece to the ski top so that it cannot deform and change the angle of the bumper wall.
A recent tour where I modified one intermediate plastic piece and not the other confirms these modifications cure the problem. The modified bumper held the red stub in place throughout a 3000 foot ascent on a mix of frozen white skin track pavement and wind sculpted sastrugi. The binding without the modifications popped out of tour mode at least a half dozen times.
There is little doubt making this mod could backfire if you grind too aggressively and the plastic bumper piece is severed in two. So caution is advised. You might want to order a spare first, just in case.