Unfortunately I've tried multiple sets of headphones with no difference whatsoever and the headphones I'm using work fine in other devices with no issues with connectivity. I'm going to try to return the controller through the retailer I bought it through, however as shown in the video, it seems to be a consistent issue across many controllers. Will keep this post updated with any progression!
Do you have any idea what the little green switch part number is? I'll try and find a replacement online if I can. The plastic part that actuates the switch works fine, as I've swapped it with another plastic switch from the same machine and it all works, but the little green buttoned switch soldered to the board seems to have gone.
I’ve taken it apart and the switches appear to be completely fine. The solder looks good too, but if there’s potential for these to commonly fail, the cost of replacing them seems to be equivalent to just buying another second hand controller so I might just do that instead.