Looks like there is a possible solution to your issue already posted. Hope this is able to help you fix your issue. https://us.community.samsung.com/t5/Galaxy-S10/Bluetooth-media-volume-sync-option/td-p/1030146
In Developer options find,
Disable absolute volume: Disables the Bluetooth absolute volume feature in case of volume issues with remote devices such as unacceptably loud volume or lack of control
Restart phone to take affect.