What could be causing these sugar leaves to be twisting/curling?

Plant looks well over fed in general, which can cause big leafy growth at the expense of bud size. Curling leaves like this can be an indication of a magnesium deficiency. Personally, I would not worry, plant is fine, just over fed though.

Most probably wind damage. Try to deduce speed or make intervals, 50 min on , 10-15 min off. High temps, intense light and overfeeding is an option too, but by twist and fan proximity - i guess its wind damage.

It looks like your fan points right at the plant. This might be a bit of that?? Or maybe part of the High N? plants looking a bit lush. I try to not let the fans blow directly on the plants but move the air around them that in turns gets in and around the buds. less aggressive. Also noticed you said you defoliated the lower buds in one of the diary weeks. with autos this size I would not take anything off them. It will only set you back. Try raising the fan height up and seeing if any new weird growth comes in like that. Old growth will not likely correct.

Try to gently look under the buds in that area -- any fuzz or slime on stem? Obvioulsy none is the preferred answer. Could also be a swing in pH, if it happened while it was growing... if it occured afterward it's not changing growth rates due to ph swings. Believe Boron def and tox can cause twisted growth. This would more likely be pH related as trace elements are usually in a soil or part of a soilless fertilizer regimen, but never know. some manufacturers with marijuana branding are completely incompetent, lol.