I may be reaching, but I noticed what I noticed.

Season 4, Mike told El she was being ridiculous when she told him the way he looked at her made her feel like a Monster. Then of course, El in a move that will possibly be confirmed as an official break up, sent Mike a note that said “From El.” In the next episode. spoiler season 5, Nancy told Jonathan he was being ridiculous when he asked her if he’d done anything to piss her off. The next episode, he offered an “un proposal” and tosses the ring aside. The Duffers confirmed that as a break up. I have a mix of Byler hope and Byler skepticism right now.