Catalina and multiple Users with same Apple ID

Finally worked out that Catalina can't handle multiple Users (on the same machine, but should be irrelevant) with the same Apple ID. Wasn't a problem before upgrading.

If I allow one user to use Keychain, it kicks the other one out of Keychain:

– So I either have to have one user without Keychain - and System preferences continually warning me some iCloud services aren't available...

– Or I have to re-authorise Keychain for each User every time I switch into the account, which takes three password prompts, plus that's something I need to do constantly throughout the day for work.

A lot of users have complained about the constant request to repeatedly sign into your AppleID, and I had the same issue (worse than the current Keychain-specific problem) which I solved by fully signing out of iCloud (on both Users) then signing back in...

But that doesn't fix this "one User at a time with keychain access" issue.

Anyone any idea how to fix? Does Apple even realise they've created issues for multiple Users with same Apple ID??