I began an photo engrave today after a successful one yesterday. The head began bouncing at every sweep (left sweep, bump, bump, right sweep, bump, bump, left sweep, bump, bump, etc.), which I had not seen or heard. I could not recognize what was printing. I stopped the print and cleaned the side lens on the head and tried again. Bump, bump, again. Then, all of a sudden, the side lens fell out. I stopped the print, cleaned the lens, and screwed it back in. This time I shrunk the print to something small. The bumping still occurred and the print started and began to skew. What should have been rectangular shape was not shaping up to be a rhombus slated right. Anyone have a clue? By the way, it cuts fine (see image below). All lenses have now been checked and cleaned (bottom did not need it).