Button number 4 stopped working

[JimmyCrooker]

I own 2 VKB Nxt evo joysticks.

Right hand LOT:SCG-R01 Kosmosima, VKBSim Gladiator EVO R XT2 v2.165,
Left hand LOT:SCG-L01 Kosmosima, VKBSim Gladiator EVO L XT2 v2.165.

My right hand joystick button number 4 stopped functioning. This is the red round button. It does not report working in VKB Device config. It is dead. All the other buttons and hats function properly. What can I do to fix this button? Should I unscrew the handle and take a peek what is going on? How to proceed?

Kind regards,

JimmyCrooker.