Quoted from EStroh:First
Put the machine in switch edge test mode. Pass your finger back and forth through the beam. Make sure it goes off each time.
Second
Check the wires to the optos and opto board. Check for a loose wire or cracked solder at the header pins. Maybe reflow solder on each just to be sure.
I would bet against your issue being one of light interference. i'd bet it's an electrical continuity issue.
Quoted from t2:Thanks for the advice! When I do this it trips on the sides but in the middle it is spuratic and doesn't always trip.
Tried adjusting the optos and using a glare guard but same results. Not sure where to look now.
I would still bet that you have a bad electrical connection somewhere. Either to the optos themselves or the opto board header. Re-flow solder to each one.