Since last update of Samsung Connect my phone (Galaxy A3 2017 Android 7.0) couldn't auto reconnect via bluetooth (e.g. with car headunit) or it was invisible to others after pairing. ScreenMirroring was also slow (connection time) and not reliable. I denied every application and spcial permissions of SAMSUNG Connect and all problems have disappeared.
Since I wanted to use other features of Samsung connect I factory reseted my phone and updated Samsung Connect. I also installed Samsung smart view. After that everything worked fine. However I noticed that if I switched off sound of media in android's Bluetooth settings my car's head unit won't connect. ( I wanted to hear navigation from the phone) But if I switched to phone speakers in Samsung Connect then it worked fine. Downside of this I have do this every time I connect to the car and I need navigation.