Network Credentials - New Twist

I have a home network with 6 machines, each of which has shared resources. All are running Win10 Pro Version 2004.

5 machines work just fine, but 1 machine, aka Hum, has a peculiar behavior.

Problem #1: When I first logon to Hum, I can access any shared resource on the entire network without entering any credentials - also, none are stored in Credential Manager. However, after a number of minutes, I am required to provide network credentials to access a share. The credentials are captured by Credential Manager & appear correct.
My question - What is happening to cause a need for credentials after several minutes?

Problem #2: If I logoff or reboot the machine all entries in Credential Manager are lost so I am back to problem #1.
My question - Why is Credential Manager loosing the credentials?

Additional info: The above behavior is only for 1 user account. I have another user account on Hum which works
just fine. Both accounts are set up identical as far as I am able to determine. Clearly there is something about the 1 account that is weird, but what?

Any help will be much appreciated.

TIA, Joe

Hi what if you make another account besides the one that works does it work correctly? the account could be corrupt.

Thanks for the reply. The machine, Hum, actually has 3 user accounts - 2 of which have no problems. I do agree the 1 account must be messed up in some way. I had hopes there might be a way to 'un-mess it up' because it is my primary account with a lot of personalization - nothing that cannot be replicated, but just extra work to set up another account in the same way.