Hi David,
Based on your version and this message it looks like you have either assigned a target to an individual transition type that already belongs to a transition simulation group or you have assigned the target to a transition group that is not defined as a transition simulation group.
If your target is assigned against a transition type, i.e, in the Transition Targets you have selected something like “Thinning [Type]” as the Transition Type/Group, then:
1. Check what transition groups this type belongs to under Definitions | Transitions | Advanced | Transition Types by Group
2. Next check if any of the groups this type is assigned to is a “Transition Simulation Group” under Definitions | Transitions | Advanced | Transition Simulation Groups If they are there then the target should either be assigned to this transition simulation group or the Transition type needs to be removed from this group, or the transition group needs to be removed from the transition simulation groups.
If your target is assigned against a Transition Group, i.e, something like “All Thinning Transitions” then be sure that the group contains all of the transition types that you want the target to apply to under Definitions | Transitions | Advanced | Transition Types by Group and be sure that the Transition Group is assigned as a Transition Simulation Group under Definitions | Transitions | Advanced | Transition Simulation Groups.
If you are still having challenges with your targets after this you could send me your library and I can take a look.
Thanks,
Leonardo