barking up the wrong tree
If your ejector plunger and/or hole was the only problem, then you would have no problem extracting the shell. When the bolt turns, a shell that is not sticking in the chamber will ROTATE WITH THE BOLT FACE, especially if there is a sharp edge to grab at the rear of the shell.
A shell that is sticking in a chamber due to roughness, dirt, rust, etc. will not rotate with the bolt, and then might leave brass there in the bolt face. This would make the bolt at least a tiny bit harder to turn as it scrapes brass away. Any deformities of the brass during the handling from firing, to collecting off the ground, to de-priming, to etc. etc. can add minor imperfections to rim edges, belts, and other parts. We might expect that the new box of shells avoided all of the reload issues.
I hope and expect that you avoid rough handling, resize the brass properly, and do not use excess pressure loads, since you probably know that they are vital to proper reload performance.
One of my articles dealt with a customer gun that had a severely stuck shell due to his neglect at the loading bench. He got distracted when changing powders, and failed to reset the powder weight measurement. If it had gone the other way, he would have had lower velocity loads. His luck went the other way, and the excess pressure made a bit of brass flow in the boltface surround.
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pictures are page 2, article text is page 1