reroll / rebuild older permissions?

Hi,
it seems, that OG-User-Roles sets "Default role assignments"-permissions in 4.x dev exclusively by subsripting to a group - not dynamically as it did in older versions e.g. 1.5.

I have existing group members who have subsripted to a group before I set "Default role assignments" to a group. Setting "Default role assignments" later does not give them permissions. Even "rebuild permissions" doesn't give them permissions.
I found no way to let users have that OG-Rules, when they subsripted earlier...

What will happen, wenn I update module in an existing site from 1.5 to 4.x?
I fear that all users lose their state...

Is there any way to reroll / rebuild older permissions?

Thanks in advance,
Ralf