On the behalf of my experience,
when I resently update my phone with new September security patch update, delivered in Pakistan 🇵🇰 some days ago. (December updates)
You need to restrat your phone 3 times.
First when update installation was completed rebot the phone some app might not work properly without rebot.
Then after using some time you need to restrat the phone agian, some settings changes, battery drain issue occurs.
Then use your phone onward.
If you see any issue then agin rebot the phone.
Thus, after 3rd time, phone will work properly.
Mine also worked