@MikroKid66: If I understood you correctly, you want to create new user with full access. You want to give him access via all mentioned services, but it does not work, right? (If I misunderstood you, let me know and probably ignore rest of my answer).
To be honest, I have never had such issue and I do this with every new device as part of default script after config reset. Disconnection is commonly caused by unstable connection. (either due to network or cpu) I tried to simulate this behavior by removing policies but I never achieved person being logged in and then disconnected. If user does not have access rights, he is simply not allowed to log in at all.
Due to that, I do not think it has something to do with your user settings, but to make sure, could you please do command
/user export hide-sensitive
and send us result? Feel free to change usernames (or any other personal info) to for example "USER_1" "USER_2" etc...
Are you trying both users from same computer, ideally together? (for example two winbox instances next to each other, one with logged admin, second trying to log in the new user). In order to find the issue, we should rule out each possibility one-by-one. Suggested test with two winbox instances should rule out network instability.
Let us know result
Meanwhile, I will keep my fingers crossed that you find the issue