GDD prover generates a non-DAG proof

[kovzol]

It also causes a stack overflow in the GV-visualizer. The issue can be found with the following statement: To prove: E, O, O1 are collinear (see the attachment). This can also be found among the Fixpoints. Now steps 16->...->50->16 build a loop in the proof which is clearly an error.

OMO-2.gex.zip

To reproduce: change boolean drawStructure to false in PanelProve.java.