Cause

The connection is faulty since it leads back to the same target without encountering another target. Such a situation is, for example, given if you connect a function with the first target of a T-node and lead the second target of the T-node back to the shared connection point.

Solution

1. Interrupt the ring situation by breaking up the connection or by inserting a function as the second target into the ring.
2. If required, start a new check run.