From what I can gather here, you seem to not be using a proper Minecraft Server Jar file.
Enough Said. Here’s the solution to your problem (you may have to click on the following post to view the whole thing)
Wasn’t that difficult to figure out 
>.< lol It’s unrelated to the UI, because the UI does it’s job of running the jarfile (or the UI would’ve probably said that starting the server has failed).
Extra info:
From knowledge and similar experiences: attempting to run a non-server jar either does not work, or does not work correctly (usually will not work). An example: back before the Node based UI was ready (when everyone was mostly on Python based UI) attempting to run Spigot’s BuildTools from the UI as a server would not work, I haven’t attempted this on the Node based UI since it does have it’s own dedicated section, although I still run that via commandline. Attempting to run Spigot’s BuildTools from the Python UI as a server would essentially throw you the same “problem” of “not starting” or “starting then stopping”. I assume the same would occur when trying to run a raw forge jarfile (universal forge, or forge installer) does not work and will give you the same “problem” because of it being an invalid Minecraft Server Jar file and needing something extra to work.
In the end: It isn’t a bug in either one of the UIs, and is just jar requirements.