smb write access not working after updating to iOS 18

I use some Samba/SMB shares, mainly on a home server and also from my router (Fritz Box).

Both SMB shares now have access issues with iOS 18.

On an iPhone 13 with iOS 17.7 there is no problem having read and write access to the same folder and shared folder, but on my iPhone 14 with iOS 18 I only have ready access...

I tried to set up the connection completely from the beginning and also set the minimum protocol version on the server side to SMB3, but nothing changed.