No sound on left speaker, but only when using Bluetooth

The speaker on the left sounded weaker than the right one when using Bluetooth.

My solution to this problem was to tweak the sound settings of my phone until both sounded the same.

Then one day, the left one simply did not work at all. Some sound was heard, but it was very little, and when I changed the sound balance of my phone to the left, and then turned up the volume, it sounded distorted.

This only happens on Bluetooth. When I use aux,both sides work perfectly.