I'm thinking the Steve we see dancing with Peggy is a Rescued Steve, not Our MCU Steve that left to restock Stones. Our Bucky is but one of a multiverse of Bucky's, and some of them were retrieved by Steve that went to restock Stones, and some of them by some event however many degrees separate from Our Steve restocking Stones.

What I'm not sure, is how them Sending Steve was supposed to work, since he had a number of different times to go to; was the Time Stone his transfer? And it was good for as many trips as long as he held it? How is he supposed to put the Soul Stone back? Can he use it to rebuild Vision?