Ok - result is same. After setting new profile, saving 2 new paswords, restart, back into new profile, Passwords not saved. In main profile there are 13 passwords that do return. Out of aprox 350. Which have to be reloaded from USB.
Upon startup, Brave Browser runs through some integrity checks, the results of which, cause Brave to sometimes decide to perform some degree of a reset.
That can cause a limited restoration of the previous state known to the user - for example, what you experience with only seeing a restoration of a limited number of passwords.
Use the following command line entry that works on the Mac, as a guide:
open -a "Brave Browser" -n --args --incognito --no-experiments --disable-extensions --user-data-dir="$HOME/Desktop/BraveTestProfile01"
On a Linux OS machine, the command to use is probably one of:
Brave Browser will launch and create a new user directory including a new Default folder that contains the user data for a new Brave user profile ← entirely independent from your existing user data.
So, you will be testing an entirely new home of user data, while using the installed Brave Browser application.
If this test works - meaning, Brave runs and you can save passwords (test a few, and they remain as you expect they should), then your issue is some kind of foul up in your existing user data.