I am using dot with graphviz version 2.47.0 (20210316.0004)
Using windows 10 home edition with 16 GByte.
Command is: dot -Tpdf extra-arrow.gv -o extra-arrow.pdf
I have a graph with 4 nodes and three edges in a nested cluster. About 75% of the time the graph seems to be rendered correctly - although I find it odd to see two arrows lying on top of each other so that one line goes through the arrowhead of the other line. About 25% of the time there is an extra arrow.
This looks like a bug to me.
Here are the links for the .gv file and two flavors of the .pdf
Ahh, being a new user I can have only two hyperlinks, so I will post the odder of the two ,pdf