Lockscreen Bypassed When Reinserting Sim Tray

Was wondering if anyone has inputs I can try. I have an S21 Ultra from my carrier. Whenever I have a sim in the sim2 slot (sim1 can have the postpaid sim or a prepaid sim from the same network) the phone would bypass the lockscreen. After several seconds, it would unlock the screen and go to what was opened before it was locked or to the sim card manager in settings if the sim in sim2 is from a different network. 

* password and fingerprint on, no face recognition

* i have done a factory reset with no remedy

* sim lock helps but doesn't help when a different sim is inserted

* the unit is carrier locked on sim1 and a knox configure profile of the carrier has been applied to it

This to me is a security vulnerability as the lockscreen will be made useless should the phone be stolen or if someone wishes to just mess up the phone and delete stuff -- stuff that do not need a password input at least. 

I've checked with Samsung support and while we tried a few things that didn't help (was told to uninstall Knox which was not possible, tried sim lock, made sure face recog wasn't enabled), I was essentially told they can't do anything about it. The chat rep suggested I reach out to the carrier who then referred me back to Samsung. 

I'd really appreciate what info you can provide as I have nothing else to try on this supposedly secure phone. 

Thank you. Apologies for wall of text.