I have the similar problem. I can connect in one office, but can not in another (they use the same authentication options). DarkyRom is working ok, so it is miui related. Generally speaking, miui do not fully support LEAP, that may be the case.
In 1.9.9 there was a general problem answering the call using the bluetooth headset - when you answer the call, call audio will be switched to the phone and you will need to manually select bluetooth to re-transfer it to your BT headset.
1.9.16 fixed that, but one other issue (also...