Alright so I have installed Azek a few times and have had the same issue each time. The stuff shrinks and never returns to its original size. I have rabbited the joints and glued at butt joints but when the fascia and the rake come together that is where the smooth side of one of them comes into the end of the other. The glue doesnt want to hold there. Cutting a 45 and getting it to look right isn't the easiest thing to do.