Switching Regulator[AP65211A] Issues: Higher Voltage then expected at minimal load, drops to 0 with small load
I don't know if I should delete this one out of shame, or leave it here for anyone else to learn from...

I didn't actually ground the GND rail on that sub-sheet... So it was left floating, after running a jumper it was all good.

Larger input and output caps are also needed uF instead of nF