After some research and reach-out we came to know that when your WSS License subscription got expired, Broadcom won't break your connection of Unified Agent (UA)/WSS Agent (WSSA) to WSS immediately, but it will trigger an alert to back-end team so that when they have scheduled maintenance they can remove/disable the expired accounts (accounts which are expired for 30 days or more).
Only by then all the connections to WSS will be disconnected. Therefore, it is suggested to change to fail-open mode when it is expired since you no longer entitled to connect to WSS.
Note 1: Post license expiry, customers won't get any support from Broadcom for any technical issues.
Note 2: The expired accounts removal/disabling time is not guaranteed. It may happen within 30 days also based on the scheduled maintenance activity by Broadcom back-end team.
There is no public facing article available for this at this moment.