It's the double. He's given up 41 this year. That's 8 more than his previous career high and if you even out PA, it's 3 more than any other season over the course of 672 PA.
It's more pronounced since 2018.
2018: 1 double every 31.3 PA
2019: 1 per 28.6 PA
2021: 1 per 16.4 PA
HR rates were 1/34.6, 1/35.8, 1/35.4.
Doubles are obviously a product of BAbip, I'm not sure how to isolate out ISO from luck though.
I don't have any point, just that he's given up a ton of doubles, like almost twice as many.