Why can I hear sound from only one headphone at a time?

Unfortunately, the symptoms point to faulty headphones that need to be either repaired or replaced. However, let's eliminate other possibilities first. 

• Check to make sure that your headphone plug is inserted all the way into the recessed jack on the Thinklabs One. If the plug does not easily and snugly fit into the jack, please use the headphone adapter included with the One.
• If the problem persists, insert the headphone plug into a different source to verify the problem. Alternatively, plug a different set of headphones into the recessed jack on the One.
• If the problem persists, send the stethoscope in for repair.