So here's the scenario:
As part of our (custom) integration with our CRM, we have a smart campaign that looks out for particular field changes, then adds the changed contacts to a static list, which I will call 'Updates for CRM' here.
At set intervals, our integration collects the information from the 'Updates for CRM' static list, updates the new information to the CRM, then removes the contact from the list.
However, occasionally there is an error, and this means the contact is not updated on CRM and stays 'stuck' on the 'Updates for CRM' static list.
What I would like is another list, smart or static, that shows contacts who are 'stuck' on the static list. For example 'contacts who have remained on the static list for more than one hour'.
Examining the 'Updates for CRM' static list itself is not an option, as there are always tens of contacts on there waiting to sync, and apart from manually noting them, there is no easy way to track how long they have been on there.
I thought the 'Not Was Removed from List' filter was the answer, but when I tried that it just created a list of everyone who had ever been added to the 'Updates for CRM' list.