A z probe is no endtop. Both are handled differently. In some special cases you can handle it as zmin but it is never ideal. z min stopps when triggered and that is z=0. That is the definition of a endstop. You can go up a bit from triggering point also that would mean nozzle was below bed.
I'm a bit puzzled here. You have the trigger in the nozzle right? So you heat up nozzle and the do homing and that should trigger only when you hit bed + trigger distance. Then you go ENDSTOP_Z_BACK_ON_HOME mm up again to stop at 0. So ENDSTOP_Z_BACK_ON_HOME must be too high or you are
using a cold nozzle and the old plasic causes a trigger to early. That is why 0.92 has now a new homing order Z up xy preheat Z
to overcome that problem. Hope you use it.