Found an old PS360. Could use some help!

So I was digging through all my old stick parts and found an old Akishop PS360 (not the + version) -- plugged it into my PC with no buttons attached and the PCB seems to work, except the triangle button shows as always pushed.

Did some searching and found I can fix this by soldering a resistor between the VCC screw terminal and the triangle button screw terminal.

Could someone better explain why this works/if there is a better solution/what size resistor I should get?

Thanks!