Image shift when locking the focuser "trigger". I didn't notice it much with the new FSQ-106EDXIII I had, if at all, but many others have. I think it is a lot more to do with focuser play due to age/use, so a new one won't necessarily show it. Routinely tightening the draw tube tensioners (4 on top of the casting) may alleviate this shift, but of that I am not certain. The teflon pad these tension is not an indefinite resource - it will wear microscopically each time it is used, causing changes.
The teflon pad on my Tak FCT-100 had not been adjusted since new (unless the prior owner resealed with lacquer each time), and needed some adjustment to prevent image shift and also improve the in/out drawtube tension and feel. It's a 28 year old telescope - maintenance was required
