12
Strange double line due to misaligned mirror
(lemmy.sdf.org)
Turns out a misaligned mirror made the laser hit the lens in a weird way, and then bouncing off something on the way out to produce this double line. Probably. What kind of strange troubleshooting have you done and what was the reason/fix?
Backlash is the play in the gear train. It would be evident if the cut was made one direction then the other. Seems like you had a different problem. Never seen that before.