I have tried SMB version 1 (CIFS) (TP-Link and Netgear ReadyNAS) and SMB version 2 (Synology) and SMB version 3 (MS Server 2016 and MS Server 2019). No matter what version of SMB it never remembers username / password.
I would like to turn the question around - since you claim not to be able to recreate the problem -
What SMB device/software are you testing om? Then maybe we could all just use that?