Can anyone confirm problems by using Bluetooth to play music on another device.
Bluetooth in combination with WiFi is problematic on many S4 Minis. You can try to flash a new Baseband.
Here is how it works:
https://xdaforums.com/galaxy-s4-mini/general/modem-samsung-galaxy-s4-mini-gt-i9195-t3390780
Good luck!