I just got my egg-bot last week. I assembled it a few days ago. On the pen arm, I didn't secure the pen-side of the arm securely with the two little screws. They seemed tightly secure, but on the 3rd or 4th egg, there was a slide-wobble, and I watched as the pen slid in a manner that was Not Acceptable™.
On went my glasses, I shut everything down, dismantled the arm, and found that the screws, indeed, were not OMFG tight to the hinge. Yay, me. Now, I just have to master setting the object-to-be-drawn-on-shape setting.
But YAY, ME!