You might want to look at your spring on the extractor - idea on Lee Enfield is that claw grabs case rim to extract, but presses case rim hard against left raceway - usually can see the milling for that - often times, the brass is flung clear, well before the fired case rim gets back to the ejector screw. I think that claw is going to extract - is that spring tension that is going to eject that fired case.
I believe the original design was to fill the magazine with chargers - then, as bolt is operated, the case rims slide up behind that extractor claw - only when single loading is that claw forced fully right to get over a case rim - I do not think that was intended as "normal" operation - but we all did that - cartridge into chamber and then close bolt - because it worked - until it does not. I have not experienced what you describe, but would be my suspicion - that spring got weak / got broke, etc. Your extractor claw was supposed to put some force to the left, as it extracted the case.
Somewhere I read that the ejection screw protruding into the bolt raceway was to eject "unfired" - i.e. heavier - shells from the rifle - too heavy with bullet still in place to get "flipped away" by the friction of the left side.
