I also have same issue with Dell U27270QM purchased in  Sep 2020 ( Manufactured in May 2020). I called up Dell Tech Support today and they said they will replace with a similar monitor. But since 30 days have passed I would be getting a refurbished one (opened I was told by only Dell personnel to test and make sure it works fine). My replacement one too may have same issue based on discussions there. It looks like the Monitors U2720Q and U2720QM have some sort of defect. I came across that discussion only after Dell Tech support person placed the service request for my replacement which I was told will arrive in 2-3 business days based on the U2720QM model availability. Deeply disappointing with dell not addressing this issue with a permanent fix.