The problem with ProcessFlow non-persistent variables.
What the heck are those? When you run a Query and reference that Query later within your flow - Query_FIELD_NAME - those are non-persistent variables. Persistent variables are ones you create on the Start node or are passed to your flow from a Service.
So, what's the problem? Apparently non-persistent variables are cleared out after you come to a UserAction in your flow. If you need to reference these variables after a UserAction (and who doesn't?) you will need to create persistent variables and then Assign the non-persistent variable values to them.
I like to use variables in my User Node notifications and have them available later in my flow so I'm going to have to start making them as persistent as I am.
