OK, before anyone here starts laughing, just hear me out on this. If at least once, like me, you've cut a tenon that was not exactly parallel with face of the wood, perhaps it was because the fence was actually cocked a little and not exactly parallel to the bit oscillation. The fence rides along two half-dovetail rails, and is supposed to square up when the tightening lever squeezes against one rail, but suppose, just suppose, you manage to unintentionally wrack the fence so it's cocked, high-centered on the track, then the lever is tightened and the fence doesn't get a chance to completely square up first? Then, during the course of cutting tenons, the fence gets jostled enough to finally seat where it should have been, and suddenly it's loose. Try this: Set your Domino so the business end is facing away from you. Now with the fence raised, slide the thickness guide to, say 40mm and slide the fence down on top of it with your left thumb. Now, flip the fence-tightening lever all the way counter clockwise, as loose as it will go and press down on the right side of the fence which is unsupported and free-floating. Feel the deflection? Your fence is now not exactly parallel to the bit orbit. If you tighten the lever while the fence is kept cocked like this, it can sometimes stay that way rather than self-center in the tracks like it would if there was no downward pressure on on the right side. If you have calipers, measure both edges of the fence to the base. Equal? If not, once the fence finally pops into place during use, it could possibly produce a loose fence condition that may in SOME (but not all) instances be perceived as a stripped or broken part. Just a theory, but I've made it happen, and if you cannot actually find a broken part, it might be time to take stock in what I'm saying and start loosening the lever only enough to slide the fence easily, avoid loosening it excessively as this introduces the slack in the tracks that can cause this situation. Next, only push down on the sliding thickness adjuster side (left thumb), not the lever side that is unsupported and free-floating. This will also help avoid cocking the fence. And last, instead of just pushing down on the end of the lever with your thumb, try backing it up with your forefinger underneath; more of a knob turning motion, with your thumb on top the forefinger on the bottom, and turn, not just press down. In any case something to try before sending your Domino in for repair.
Gary