Upgrade to 5.6.1.2 caused site to not work - fatal error thrown about AddBlockBlockTypePermissionAccess::isPermissionKeyInUse()

Permalink
Hi
I have a site I upgraded from 5.5.2.1 to 5.6.1.2 and I get the following error no matter if I upgrade via system itself OR if I upload and unpack upgrade then run upgrade from c5 interface.

Fatal error: Call to undefined method AddBlockBlockTypePermissionAccess::isPermissionKeyInUse() in /home/ybdcom/public_html/updates/concrete5.6.1.2_updater/concrete/helpers/concrete/upgrade/version_560.php on line 284

The site renders my stacks as invalid for some reason.. can't work this one out!!

jolly