Something is def not right with the check valve in the stone. It could have malt glued itself open. You will not know until you can take it apart. I would put a check valve on your regulator so at least the rootbeer will not flow into the regulator until you can get to the valve on the stone. Check the spring and seals in the stone valve when you can get o it. Godd luck.
CBO "Chief Brewing Officer" / Zymurgist
Bluegrass Brewing Co
636 East Main St