I've just submitted v2.2.2 of One-Page Checkout for the Zen Cart moderators' review; I'll post back here when it's available for download.

This release contains changes associated with the following GitHub issues:

#222: Establish compatibility with "Ship2Pay" payment method.
#223: Correct parameters passed to zen_address_label.
#224: paypalwpp, correcting PHP warnings on address-creation bypass.
#225: Establish compatibility with "Ceon Sage Pay Direct" payment method.