A work-around is suggested below. The work-around is not guaranteed; it is a suggestion which seemed to help for the particular use case but it has not been thoroughly tested so other side-effects of operations could be discovered. Please seriously consider the "Important!" note below.
In the mentioned use case, the work-around is to ensure that the access types being used across the contacts include more than one role.
So, for example, if the access type for one contact is the Employee Access Type, which has only one role, which is the Employee role, then you could add a second role to the Employee access type. The second role could be a separate copy of the existing Employee role.
Consider that adding a role to an access type affects all contacts that are assigned to that access type.
Important! Please re-consider your business case for de-installing the force_unique_userid option. Keep the option Installed to avoid many other problems for which work-arounds may not be possible and for which a product fix would be highly improbable.