From the evidence available to us, it appears that the pilots were unable to initiate that levelling out, but something clearly did.
Today I discovered an Electra manual that discusses a rudder/aileron linkage. Apparently rudder movements affect the ailerons independent of the control wheel. It's part of a mechanism to help make balanced turns. There's some exploration to do here.
This project is far from over. I'll have a new version out in a couple weeks, covering the Chicago Tribune materials and some ideas developed from our conversation here.