If I was you, this is what I would do:
Set my sights to mechanical zero. Attempt to zero at 50m and see if the 50m zero cures the problem. If not then I would consider removing a few .001’s off the front sight post to achieve the correct 50m zero. Sorry, can’t offer any more help than that.
Anyone else?
ETA: Here is an example of the trajectory of the M855 round taken from the Army Marksmanship manual. Your ammo used for zeroing will probably differ from the M885, but this chart gives you an idea of how the bullet path rises from 25m out towards 50m, peaking at about 175m. If you notice the POI compared between 50m and approximately 275m you will see about the same POI.
The difference between a 25m zero and a 50m zero on this chart appears to be about a 4.5-5.0” difference. This is why a 50m zero might benefit you.