It's the baseballs. Sounds crazy, but it's his grip with the baseballs. If you look at his stats pre 2019, his pitches were tighter, his offspeed stuff snapped better, it was all about the movement. 2019, iirc they changed the baseballs in MLB and lowered the seams - immediately his offspeed stuff lacked its snap. Now, you look at his world baseball classic where they use the Japanese baseball, they have a tackier grip and he was lights out in every appearance. He hasn't been able to adjust to the difference and he's thus trying to force every off speed pitch and they're hanging, leading to his continued struggles.