Mimaki CG130 FX Registration Problem

Recently my 54" Mimaki plotter began misbehaving. It will not read registration marks printed from FineCut in Adobe Illustrator CS5. The error is simply "err36 Markdetect" while searching for the first mark.

Things I have attempted to remedy the situation:
1. I have run a laser position calibration.

2. Verified all settings in FineCut and plotter are correct.

3. I have removed the cover and attempted to remove the sensor so I can see underneath in case a small piece of vinyl is obstructing the laser but the two tiny screws are installed so tight I have to assume they used lock-tight on them. One screw I was able to remove the other stripped.

Any help would be greatly appreciated. I would gladly replace the sensore as well if I had any info on a parts supplier for this machine.