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Check the belt tension, fasten if necessary. Loose belt will cause incorrect movement. Check the mirror and lenses, fasten if it loose. Loose mirror or lenses will cause zig zag patern, because the beam is not steady and fibrate during operation.
I think your beam setting is not correct. The laser beam is not pass though the air assist hole completely, so it create a second reflexing beam. I hope this info helps. Good luck.