So just to confirm, you can manually cycle a full magazine of the Wasp reloads, and cycle rounds out after firing one or more, so long as the magazine is seated in the rifle? ONLY when the magazine is dropped does the loaded, unfired round fail to eject?
That sounds to me like an issue in the action TBH. If it had anything to do with the chamber, headspacing, or sizing (specifically lack thereof) of the rounds, it would be consistent regardless of magazine, no? It is bizarre that other ammo doesn't do the same though, which contradicts that thought process.
After you fire that last round that won't eject manually, does the spent casing eject normally?
Edit: I know this might sound weird, but next time after firing a few rounds, try pulling the charge handle back a bit to see if the loaded round is "free" in the chamber with the magazine still seated, bring the action and the same round back into battery, drop the magazine, and check again to see if it's jammed. This should tell you for sure if it is the rifle or the ammo. I can't imagine the magazine really having anything to do with the stuck round, but this should tell.