I promised a little while ago to get back if I found the edge cases making node edit forms to malfunction. I now have some more information on the issue.
It seems that only node form contexts created with arguments can be rendered by Panels – which for me implies that CTools has some problems with context loading. Three cases compared:
* Edit forms added as contexts at the path bugreport/%node-edit – works fine
* Edit forms added with relationships, from a "normal" node context – works bad, output is "Form goes here".
* Edit forms added manually as contexts, by entering a node ID – works bad, output is "Form goes here".
I hope this may shed some light on the issue.