Weak Bt Signal Mi5s Plus

[GacekTV]

I've noticed some time ago weak bluetooth signal. Listening to music Xiaomi bust be next otherwise breaks connection. With Mi Band 2 it's the same - no notification when phone is a few meters away. I install clear xiaomi.eu - it didn't help
From what can it be? The phone fell a few times - is it from this?
How repair this? How much cost new BT anten to mi5s plus?