You are correct in that the S02 is an ancillary error (you are getting that because of the S0157 error). I work with alot of RT480's and I didn't remember that specific error. I am pretty sure that error should only be generated on machines with dual heads, of which there were only a few made! This would be 2 Y axis beams with ehads on one machine, very productive, very pricey made for automated high production panel precessing. There was an error on those machines that stopped the machines if the heads were going to work to closely to one another. That in mind, if the machien data, constants or PLC has been changed in anyway in the past few weeks I am wondering if the machine is looking for the second head signal and just stopping because it doesnt see it? I would start with reloading machine back up data if you have it or obtain one from Biesse and start there.
Hope this helps!