so I have a pair of S1s.  One runs the 40w and the other the 2w IR.  also have a 10w but never use that.  Anyway, machine worked great for me for many months and suddenly it started to lose track of its position.   I cleaned it and cleaned the sensors, and they may not be perfect, but they are pretty clean. I checked for obstructions, grit, lube, everything.   I was behind on a project so i switched to my other machine and it ran fine for a couple months and now have the same issue.   I changed air assist unit, air assist cable, USB to PC cable and even swapped out the little usb piece that comes with as a spare.  Now i have two machines that do not work.

The problem:  when I go to set zero on my work piece and the machine travels back to the L bracket to touch off it comes up short by an inch and crashes the laser head into the L bracket.  If I touch off on a piece near the back of the machine it will set on the L bracket but if I repeat the step maybe 5-10 more times it eventually misses it again and you can literally see each time you hit set 0 it moves closer and closer to the edge of the L bracket until you guessed it…….Crash.  Did I screw up buying the S1 machines?