We probably need more words or a screenshot. 
Please look at the Cuts/ Layers window and confirm that you are working in mm/minute.
If needed, this can be changed in the Settings window in LightBurn.
This type of ‘Lost motion’ happens when speeds are too high and corners are too fast.
Slowing down is almost always the cure.
Laser engravers can stick or Bind if they are assembled off-square.