I mean 2016 also had a number of moments between Clinton running into sudden one off issues like that health scare then into emails, comey, etc over and over. Each one of those brought her rising favorables back to the same floor level with Trump. For what it's worth Biden has basically coasted by staying out of the spotlight for better or worse. More or less the inverse of 2016, where any time Trump came into the spotlight he dropped precipitously, but now he simply can't avoid being out there by virtue of being president. Every time he ducks low, he starts to climb but since we're nearing the end, he's in a bad way and has to compete (along with his ego probably pushing him)... it's probably going to be a rough going for the GOP into November.
Obviously none of this accounts for the bullshit Trump, Barr and the senate can pull at any time though. I fully expect something to crop up eventually.