New Desktop - Cannot Change Workflow State (Cannot Add / Remove Field)

Hi All, reporting a bug (or at least an infuriating difference!) between classic and new desktop, reporting this here as well as through our partner as it this sometimes seems to be a more effective path of reporting bugs that actually make it through to the necessary level of support!

I have a class called "Budget" which has a property "Total Value" - this property is set through a VAF script that does updates to various properties as part of event handlers, in New Desktop, when I try to move the budget to a new workflow state I receive an error:

Access denied.
You are not allowed to add, modify, or remove the property "Total Value".

However, if I revert to classic desktop and use the same workflow state transition the change occurs with no problem at all.

The odd thing is that the behaviour is inconsistent - if I create a new "Budget" and send it through the same state transition it occurs without any issue. I would love to help chase down this bug, as the VAF extension (and state transitions) are critical to us, but I can't see any more valuable error information available through new desktop!