DSXchange

The Collector and Transformer stages are active stage types (check their properties in the Stage Types branch of Manager). For whatever reason, whoever wrote the Collector stage does not allow it to accept inputs from an immediately prior active stage type. Which seems odd to me, but that's what the error message is suggesting.
A fix would be to insert a Sequential File stage on each of the 11 links, so that there is a passive stage type between the two active stage types on each link.