Help! Anthem STR preamp ARC sounds worse than when it's off

Last time I used ARC, it made an appreciable positive difference. Smooth, clean, and bass was deep.

I redid it yesterday, using 10 positions, and two subs, and it sounds much better, not louder, better with it off. ARC is cancelling out all my bass. It inverted the subs polarity, when i switch it to normal, bass comes back and is powerful.

I wonder if using 10 positions did something strange.

Note, I also used the phase testing portion of ARC too to ensure speakers and subs are in phase.

Did I do something wrong? How could it mess up this bad when it seems to have done so good on my first try a few weeks ago?

Anyone wrestled around with best practices here?