Grateful for some advice/assistance on this problem.

My earbuds have stopped functioning properly. They were absolute fine, working as expected last week but now I have very low volume in the left earbud. The sound is there, not absent.

The buds are clean and also have been updated to the latest firmware (3.1.2) via the app (8.0.1), they worked fine after that upgrade.

The fault persists, even when connected to another device. I have deleted Bluetooth pairing information and repaired, to no effect. I have also restored to factory settings as per Sony's instructions - no improvement.

I honestly can't tell whether this is a software or a hardware issue.

Any help appreciated.