It adds the keys from the master version as well. In 8.4 we added some more keys to CUVc in the master version so your 2 extra keys brought it over the limit of 80. I have increased the limit to 200. This will be available in 8.4 2017-09-13.
The register for Order Classes is common for Sales orders and Service orders. When I set an Order Class to create an Activity - it works for Sales Order, while for Service Orders - not. Is any setting...
