I’ve experienced flexure in the focuser as the OTA tracks and the camera weight distribution shifts, as well as flexure that may have been the result of cable drag as the mount was tracking.
Generally, if I am imaging at fl’s below around 1200mm, flexure tends not to be noticeable but as soon as I pop my head above 1500mm fl, unless I am very, very fastidious about tightening everything down, locking focusers, minimizing cable drag, balancing the rig, etc. then doing it all again, flexure will almost certainly rear its ugly head.
Cheers
Dennis