MacBook Pro 16" 2019, after the last update i'm experiencing serious issues with my external monitor. I have two attached, the Dell U3417W has no issues, the BenQ SW271 is having issues. res is 1920x1080 (but it is a 4k monitor).
Sometimes it works good, mostly not after the last BigSur update this week :-( (directly after the update i noticed that the monitor arrangement was messed up also).
If i detach the Dell monitor, the BenQ is getting the right res. again.