My C14 (in 2014) came with these bolts to secure the mirror. They were screwed through the back of the tube to secure the mirror fixed in place and needed to be removed or at least loosened so the telescope could be operated. There were strict instructions that they should not be used to lock the mirror during observations. Celestron said it was okay to remove them completely. (Unless the telescope was to be shifted – which was what they were designed for, they were not to be used.) So I removed them completely and stored them appropriately labelled. I covered the holes with adhesive rubber pads. I don’t know whether this has helped… Maybe they can be safely used by a responsible adult… Where to get them? Perhaps from Celestron or a dealer. You can see the ‘mirror lock screws’ in the attached image.
I seem to have very little image shift anyway, but my work is not critical.