Where are you located? My first issues and experiences with pinball machines I searched and found a local pinball wizard in my area and invited him over to help fix some issues. Most people in this community will help out for free especially if they live close to you. Easy way to meet local people in the hobby and expand your knowledge of the pin.

As far as your issue it could be a bad rom maybe or a bad connection. The dmd panel will pull straight up and you can lay it down on top of the play field to access it. I would look back in the circuit board area and remove and reset all connections and go from there.

Starting with the backglass. Make sure the top lock is in the unlock position. From there lift the backglass up by the plastic lip (it should clear the bottom DMD/Speaker Panel that it rests on). Once up pull the bottom out slighltly. From there you should be able to grab the backglass and take it out of the machine.
The speakerpanel containing the DMD should lift up. From there you can lay it down on the playfiled glass. I would check both connections going into the DMD, and from the DMD into the main board. Trying reseating the cable on both sides.

Once done, and have everything back together, I would run tests via the coindoor buttons. There is even a display test accessed via these buttons. Does the display continue to work during this or does it fizzle out? Give a try to the above, and let us know what happens.

There could be several issues causing flakiness on your DMD, so lets rule out the easy stuff first.

Did you ever resolve your issue? I am having almost the exact situation. I am waiting on a new ribbon cable to install, so I hope that's it for me. I'd be interested in how/if you resolved it.

New ribbon cable came in today - no help!

Rob