The expansion rate of nylon just isn't high enough to give the severe deflection you are trying to illustrate. It CAN'T happen, especially in the minor temp changes from one week to another.

That large of a control position change is indicative of something major wrong in the mounting of servos or something else. I'd ground the plane until it was located and resolved. Nyrods won't cause it. If the percentage expansion of nylon was that bad... they wouln't make nylon pushrods at all.

Maybe in the changing from the nyrods to solid wire you cured some other problem you hadn't noticed... such as unsupported pushrod section flexing. the difference n flexibility of the nylon at 80 deg vs 40 deg is huge! That 4 to 6 inch section between the control horn and the fuselage entry could make the difference you indicated due to flexing in a different curve at the different temperature.

Just the indication of the nosewheel being straight and the rudder being off is obvious evidence of an improperly installed control system. It CAN'T happen if you do it right.