Ishapore No1 MKIII* hard closing bolt

[Parashooter]

The videos show an extractor mortise with some burrs. Smoothing those out might help.

As for "how much should be taken off the contacting edge?" - the answer is "enough but no more". From an engineering standpoint, we really need only enough bolt face remaining to support the base of the cartridge, not counting the rim (which isn't directly subjected to firing pressure) - so one could put a fairly serious chamfer where it's jamming without meaningful reduction of the normal pressure containment system. On the other hand, there shouldn't be any increase in the visible gap between bolt head and receiver ring when the bolt is closed - since a good fit there is part of the system that directs escaping gas away from the firer in the event of a ruptured case.

But before chamfering the bolt head, at least try deburring both the extractor and the barrel mortise into which it fits when the bolt goes forward.