On most recent update, the ACR window UI is scaled up 200% on my laptop. Photoshop and all other adobe software displays the correct resolution but ACR gets massive and makes it borderline impossible to use.
I had to change my display resolution to 1080p just to be able to see all the buttons -- but I am not willing to permanently work in a 1080p environment. Pretty bad bug, I hope Adobe is able to patch it.