Mame arcade cabinet - xbox control problems

[DrZeus]

Ok, so I have built a xbox mame arcade cabinet with 2 x xbox controllers hacked apart and arcade controls wired to controller solder points.

Looks and works great except:

plays fine, after about 5-10mins of playing, one of the control pads directions on the DPad (wired to the arcade joystick) seem to get stuck 'on'.
e.g. the direction down or left is constantly being pushed without the button being closed
This usually happens only in fighting games where a lot of the buttons are being pushed (although it has happened in others).  The button will only release with a power cycle

I would imagine that it is getting grounded for some reason when it's not supposed to be. Here is what is running:

MAMEoX128_Plus ver20060505
2 x xbox controllers wired directly to arcade controls
Both original MS controller S pads
using a common ground for each pad to arcade controls (eg each button/direction does not have it's own ground)
I am using the Dpad for arcade stick directions
I am using all xbox buttons including analog stick buttons
I am using L/R triggers as buttons
Everything has been removed from the controller pcb other than L/R trigger and analog stick pots
All connections correct and perfectly soldered

So what could be the problem?
Does the controller pad use a common ground? It seems to
Is it a problem that all the buttons and Dpad are analog buttons?
As it seems to happen only/more with games that use a lot of buttons, is a combination giving me a weird ground somewhere?
I read somewhere that I may need a resistor on the two analog triggers. I currently have them just hooked up to buttons, and they do work but could that cause a problem?


Does anyone have any ideas?? I'm tearing my hair out now, can't track it down

[DrZeus]

Ok, what I have narrowed it down to is:

The problem only happens when the arcade buttons wired to the L/R analog triggers of the xbox controllers are being used.

When a direction gets stuck it is actually one of the analog sticks that is doing it.  These are still on the controller pcb but not being used and not wired to the arcade control panel.  They cannot be removed as it creates a value of x0, y0 (down left i think) and it is always pressing down/left.

Is there any way of stopping the analog stick from changing value, keeping them essentially centered?

And why is it the analog triggers that is making the analog sticks change?