ON/OFF button not clicky anymore

My 4 year old Sennheiser headphones started acting weird a few months back. The on/off button is no longer feeling clicky and requires some extra effort to push.

Regardless of push time, in 9/10 cases the headphones enter pairing mode. In the 1/10 cases I pushed the button at just the right angle to avoid it.

Upon opening them, I realised that the actuating part of the button (the electronic bit) definitely is mot as clicky as the volume up one and experimenting with a thin screwdriver bit made me realise it's a game of chance with 2/10 presses entering pairing mode and 8/10 working just right. The deciding factor was pressure. There is no blockage or problem I can identify with the exterior plastic button.

Is there anything I can do to fix it? Part of me doesn't want to accept it but it seems the actuator is soldered and not replaceable without significant investment in equipment.