Sorry for the late reply – I accidentally stopped email notifications so I didn’t receive your reply.
I tried changing the Squeezebox/Squeezelite player audio sources and Raspberry Pi settings however these do not do anything.
Is there any other way to fix the audio problem without formatting everything and starting again? This seems to be a recurring problem and it is not ideal to have to reinstall the entire system every time it stops working.
I’ve now basically given up on BT as it is not working with Squeezebox at all (even though it does work natively). I am not using ethernet as it is impractical to get a cable from the router to the Pi. Despite this, I do not think that these would affect the audio output.