Jon, the issue may simply be that you have enabled the "link" icon next to a field for a data blend, but you are not actually USING any fields from the blended data source in any of your worksheets.
Could that be the issue?
i think this might be the case since i cant find any fields with orange icon for this particular datasouce...
do i just unclick the link in the primary data source??
Yes. That should do it. I have seen Tableau have trouble forgetting that linkage. Don’t worry too much if you still send the orange check mark if you have confirmed that no fields from the secondary source are actually being used in a viz.