Both wifi and a mobile hotspot have been tested. This happends across multiple servers, both official and communities.

Hello Lonemhh.
Do you have an option to check this on wired network? As the wi-fi connection or hotspot might not be enough due to DayZ being very network demanding. This error occurs when you are too long in the login state and the connection to the server is incomplete.
Regards,
Geez

Wired worked for a little while, but not anymore. Anything else we can try out?

Hello Lonemhh.
We are looking into improvements regading to the loading int othe game for the future versions.
Can you send us a screenshot of the exact error you are receiving?
Regards,
Geez

Also, are there any vehicles or bases in the vicinity of your character?
Regards,
Geez

No. It can happend anywhere on any type of server. Both on ps4 and ps5.

Found a solution for me.
It's very simple as most of the times with Dayz errors.
So first you have to log out from your Steam account. Exit Steam. Restart pc.
Then Login to your Steam account. That's it.
Seems like we have been logged in to Steam for too long.
Hope this helps everyone!

^^ this is playstation, nothing to do with PC or Steam