Squiggly lines on Boss LS3655 with Lightburn

Just to verify: when you say “Both are X-Axis Movements”, the X axis is left-to-right in that picture.

If that’s the case, then there’s mechanical backlash in the Y axis, because it does not begin moving when it should and continues moving after it should stop. The squiggles are perpendicular to the X axis, which is dutifully hauling the laser head along.

There’s a loose screw somewhere between the Y axis motor shaft and the laser beam. My first guess, as always, is the setscrew securing the pulley to the motor shaft, so that’s a good place to start.

The number of times I’ve been absolutely certain I checked something, only to eventually find the problem was right there and how could I possibly have missed it right before my eyes is too large to mention.