I sent an Error Report to Samsung and their response is the following;

Yesterday i updated my S21 FE to One UI 6.1 , now i noticed the charging AOD blinks very/too much. Even the light falling upon the phone is constant i.e the surrounding light intensity doesn't increases or decreases.

Yesterday i updated my S21 FE to One UI 6.1 , later that night i started getting (Sim)Signal Problems. Like, there is signals on 1 sim and the 2nd sim is not having any signals(Emergency Calls Only). It becomes fine after Aeroplane Mode but after som...

Updated my S21 FE(Pakistani) to One UI 6.1 , so far so good.

I texted samsung pakistan about green line issue after installing an update. And their response was the following;