This is common issue of the app.
Battery drain after disconnection is happening to another devices as well.
There's a way around it that i found, try to switch your BT on and off while the connection is established.
Though sometimes this is ...
is the controller recognized by android, and can you navigate in the menus when paired?
If not, check that you have the following:
- official MIUI Rom
- Magisk with modules: 1controller, Sony framework yes i have but m talking about ds3...
That's why I said "not a guarantee".
confirmed on pie too check here