was just reminded of this today. wow, time flies. sorry for the delay, but if you’re still trying to solve this, you can use this solution:
Call HandleRotation in tick. Then input is used to open a gate that adds local rotations to both the character mesh and spring arm simultaneously giving you a seamless rotation through the poles. Have done something like this in the past (but using desired rotations and RInterpTo’s), but just to be sure, tested this in the top down example (and making the character flying to simplify things) and worked out ok with full upside down camera support.