Signaling between instances that don't belong to your tree shouldn't really work properly.
When you instance a scene then you must add it to the tree with add_child(variable_with_instance)
Maybe that is the source of the problem? If you upload a project with the problem I could take a look and help you understand it.
Damn I never had an issue with signals, but this was not clear in the documentation. I have a C# background and I've been kinda treating signals like events. I guess it was a coincidence I didn't have any issues with them, then again there were a bunch of bugs in my project and I used signals a lot so maybe this was the issue with some of those bugs.
