ScreenSharing autofill userid/password can't be changed
I have a head-less MacMini (mid-2010 running High Sierra) that I use as a media server. I control it via screen-sharing from my Macbook Air (running Catalina).
I invoke it by "Go -> Connect to Server" within Finder. A popup comes up with "vnc://IP_ADDRESS" (IP address of the Mini). I select "connect" and a popup comes prefilled with an old userid and password (for my account on the Mini). If I change those to the proper values, it connects sucessfully.
However, the new and correct userid/password do not stick. Next time I try to connect, the old and incorrect values are prefilled.
I have tried going to KeyChain Access (on the AIr) and deleting any entries for the Mini. The problem persists.
MacBook Air 13″, macOS 12.0