Ok, it took me a few tries to recreate. I thought it might be customizing the form, or the template I used. I honestly could not remember the steps. I can only say I think this is the problem, but it produced similar results.
I believe what I did is, in a site that is set to document relative links, I set the action to a site root link because of how the form would be used in the web site (/apps/contact/sendMessage.php). Also note that, at least in my test, the target page did not exist yet. The extension creates the target page in the correct location, but does not put the correct values in the redirect of the target page validation and does not put the correct value in the validatedField function of the form page.
Understanding the problem now, it can be worked around, but the extension could also detect the type of action entered by how the link begins (/, ../, or filename), especially since it creates the target file in the correct location. I forgot to look and see how the action in the form came out, but I think it was correct.