Strange cluster display


I could not find anything about this kind of display of gh cluster:


It is a cluster with a lot of input and output and it seems to work properly (not entirely my code) but this display suggest some type of warning. Additionally it makes harder to work with this cluster - you can use right button menu there and check parameters names or use any gh tools, but it is hard to point in proper place without normal display :). Any suggestions what is going on here?

I think the cluster is referenced to a file on the disk and that file has gone missing (so the cluster is using the last cached version).

There should be a message to that effect in the cluster tooltip: