User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/86.0.4240.112 Safari/537.36
Steps to reproduce:
I entered a new contact to my existing address book.
In the inbox the sender's name of that address remained as it is in the email header rather than changing to the Display name I entered in the address book.
Former versions upated this latest when I clicked onto another account or folder and returned back to the initial folder.
Now I have to go to settings - general - reading and view and have to remove the tick from the box at "Only show display name on known contacts" and tick it again.
Then the changes apply.
I hope the wording leads you to the right place in the settings, I am using the German version
After entering a new contact to the address book and defining a display name, this should show up in teh mail folder instead of the sender's data in teh email header