I would guess actual polling error or “polling error” based on the fact that campaigning really hasn’t started in earnest. (Biden is still hiring senior staff in Pennsylvania and Trump hasn’t even opened an office there yet.) We should probably expect polling to be all over the place before late September or so, especially with cross-tabs and the tiny sample sizes. Barely anyone is spending the money for high quality polls yet (except maybe the campaigns but they don’t release those).
It’s obvious that there’s real anger about the Gaza war crimes and inflation (which no president controls but people think they do). But a lot of young people are genuinely undecided. If it’s your first or second presidential election, you inevitably make your mind up later than if you already have a party.