Avengers Endgame and a certain missing weapon [SPOILERS]

Heads up: this is about a specific plot point in Avengers: Endgame. Do NOT read this if you haven’t seen the movie yet. You’ve been warned.

At the end of the movie, Cap goes back in time to return the stones to their original timeline. He takes with him his shield and Thor’s hammer: Mjölnir.

Cap doesn’t return from the trip as planned,  and the crew notice an old man sitting on the bench. At this point Old-man Cap gives his shield to Mac. Very nice and touching scene. But, where’s Mjölnir?

One explanation I like is that during Cap’s time travels to return the stones he returns the Power Stone last, to 1970, and that’s where he stayed, with Peggy. At this point, there would have to be two Captain Americas in the same timeline that the MCU has traveled for the past 10 years. The Old-Man Cap decided to live with Peggy, in seclusion. (He couldn’t exactly go out and advertise who he was, could he?)

Update: in the comments Chris Estrada points out that Cap almost certainly goes back to the 1940s to be with Peggy. I highly suggest reading his entire comment. It sheds a lot more light on this topic.

If this is what happened, then Cap would have taken on a role of a average, nondescript citizen, and he would have to have an agreement with Peggy not to influence the timeline.

So here’s Cap, putting down his hero persona and living as a regular citizen. He has his shield and hammer, probably stored away in the hall closet. But at some point, Cap is no longer “worthy” of the hammer; he’s mowing the lawn instead of fighting the good fight against evil.

And so Mjölnir sits, unmovable, in the hall closet. I picture a scene of one day Cap goes to pick up the hammer and it doesn’t budge; he suddenly realizes he’s no longer a hero.

Unfortunately, none of that works for the continuity of the timeline. Because Cap would have to have left Mjölnir back in Asgard to replace the one that Fat-Thor brought back with him. Basically, they borrowed Mjölnir from the past to fight Thanos.

The big problem with Cap going back to live a life with Peggy — Peggy was already married and had a child with another man. We know that from an interview with Peggy shown in Captain America: Winter Soldier, recorded in 1953. We can say that maybe Peggy and this man were no longer together by 1970 when Cap went back — that’s believable. However, again in Winter Soldier there’s a scene with Cap and old Peggy, and she definitely doesn’t remember a relationship with him after he went down in the plane in the arctic.

The only way this works is if Cap told Peggy what would happen in the future, that he would be thawed out of the ice, and at some point she would have to convince young Cap that they never had a life together.

That’s some serious fan-wanking, but pretty much every single story that involves time travel requires those sort of blinders. Don’t pull too hard, or the whole story unravels.

I’m not complaining. I think Endgame did a fantastic job of injecting time travel into the plot in a playful and thoughtful way. But it’s not flawless. Clearly, this wasn’t the plan all along, because if it were they could have added a few tiny easter eggs in the previous movies that only hatch during the time travel scenes.

What do you think? Are there any other temporal paradoxes that the story glosses over?