Be aware that there - unfortunately, are TWO standards for the four-pinned 3.5mm with microphone, I do not know if the wrong type could cause this.
The OMTP and the CTIA. Now most devices (including Pro1/Pro1X) uses CTIA, some years back most (e.g the real Nokia) used OMTP. OMTP is an a LOT more sensible standard BTW, having ground close to a plug housing that could be metal.
The easiest way to know if a given headset is CTIA or OMTP (if doc does not tell), is to measure the resistance between the right and left at the tip. Typically something like 320-340 Ω, then measure for he t