Another case of flexure?

[jimjam11]

A couple of nights ago I left everything running overnight and it appeared to behave flawlessly in terms of guiding etc, but I notice eccentricity became progressively worse. It started at approx 0.5 (not brilliant) and ended up > 0.9 (totally unusable). The direction of drift was always identical and looks like a combination of RA and Dec (RA axis is almost vertical in the screenshot). Guiding was consistent all night at around 0.6". Image scale was 4" pp so I assume this was flexure?

[retret66]

probably balance as it progress close to meridian flip. Maybe check your guiding logs and see if it never changes then it is flexture.  If guiding also have .9 RMS then most likely balance.