I have hacked many of these and never had this problem before.
I have modded a sega virtua stick high grade to take an official 360 pad pcb.
I took out the common ground for the ps select l2 and r2 buttons.
Have wired everything up and get a very strange double input.
When I press left the left thumbstick button is also activating (l3) and visa versa
And when I press right L2 is also on,
This has happened with both PCB’s I have put in the stick and I just cant figure it out.
There are no shorts and as its been the same for 2 pads I cant see it being a coincidence.
Any help would be appreciated.