User accounts not working correctly in HS

I have quite a lot of problems regarding user accounts since High Sierra, on a 2016 15" MBP (touch, 16GB Ram).

It's most apparent in fast user switching problems, but this probably has to do with the way the user accounts are handled by HS.

Since the update to High Sierra, the user account, from which I switch to the secondary account, regularly crashes completely. The account which I switched to, usually loads normally - but apparently the previous account sometimes hangs in the middle of nowhere.

To be more specific: I switch from account A (which is an AD account) to account B (a local user account); account A regularly (about each 3rd or 4th time, at fast user switch) crashes. After that, account A isn't displayed in the fast user switch menu, top right, as logged in anymore.

When I switch back, to log in again to account A, usually the profile loads normally.

I one case though, the user session was still "half" there, and I got lots of errors - regarding file privileges not being set correctly, etc. Apparently the account A-userfolder was still blocked by the old session, and it logs me in in some temporary mode.

Luckily after reboot, everything was back to normal - but fact is, the fast user switch function seems to be broken in HS.

Apple also executed some to me very questionable changes to the user accounts since HS, which might have to with this: local user accounts, which aren't linked to either Active Directory or iCloud-accounts, don't appear in the login window anymore. I can see the user normally in the Users & Groups prefs, it has admin rights and it's allowed to unlock FileVault - but still Apple hides the account in the login window, meaning I can't login with this account after reboot. Because of FileVault, I first have to log in with my AD account - and then I can switch to the local account, if needed; and as stated above, the AD account quite regularly crashed in this procedure.

This is very annoying, I don't understand why they ruined the code like that. Always used to work without issues, I've been working with a similar config since years.