I lost the speakers on my sordins about a year ago. They are about 7 years old. I opened them up for inspection and I had corrosion in the battery compartment that ruined the power wire from the terminal on the compartment to the board. If you open the wire jacket or can see the wire at the ends and it's tarnished or dull like an old penny generally it's no good. The copper needs to be shiny and bright.

I pulled the battery compartment apart to unsolder the wire, soldered a new wire into place and scraped the terminals clean and sealed it up with RTV. Works mint now. If it's already broken taking it apart can't really hurt, you may see something on the board/ wiring ect ect.

If I know I wont be using them for a while I pull the batteries out and I keep them under the velcro headband cover.

I think after a time ear sweat and old batteries can wreak havoc on the electronics.