Mail shows items from other folders in Inbox, and I can´t get rid of them

One of my mail account inboxes is showing emails, which are in other folders, like Trash, Sent, etc.

The affected account has folders within the inbox (which I have created server side), to manually sort after reading. Some, but not all, mails from these folders are now also shown in Inbox.

The Folder column in Inbox displays the correct folder the mail is supposed to be in (and it actually also is in the folder), but I obviously don´t want any other mail in my Inbox view except new mails, and mails I didn´t yet put somewhere else.

How do I get rid of these mails showing up in my inbox?

When I move one of these emails to another folder, it will disappear from Inbox, but will show up again in Inbox once I move it back to it´s original folder.

Additionally, the Inbox changes it´s sorting every time I go back into it, from my default new-to-old to old-to-new or something that looks rather random to me.

I´m not using the Categories function, and I don´t group emails.

I‘m on Mac OS 15.4, the problem didn´t exist on OS 13 (from which I just updated). I did restart both the Mac as well as Mail.

Thank you.