My config:
OPC 2.0.286.100415
VM 3.0.9
Joomla 3.4.1
I'm using OPC + VM3 + the Multisafepay payment plugin (multiple methods). Since a couple of weeks, creditcard payments are counted 2x in Google Analytics. Other payment methods are counted correctly. All payments are made through the same plugin.
Apparently the GA script is fired twice on the thank you page, but only whit creditcards. Strange ... any idea if OPC plays a role in this?