I’ve had a similar problem, working perfectly for 2 years (I had an additional years warranty through buying from John Lewis Uk)

The headphones suddenly started draining after 40mins use.

Contacted Sony who told me to send them off for inspection and cost of repair, as they were just out of extended warranty.

Repair estimate came to £134.76 which involved replacing both ear buds

Extremely disappointed that they are not prepared to do anything as items of such cost and brand should have a greater shelf life than 2 years