Houdini’s legacy media server is a pretty good one - https://icer.ink/.repo/legacy/media.zip
It’s also very easy to setup, all you got to do is unzip it, set up the sub-domains for it and then configure the play page (/play/index.html) and configure your IPs and ports in the javascript bit in the head section of the html page. That is all.
I would recommend using Houdini over Kitsune, it is an emulator written in python2.7 and has complete handlers for the AS2 client. I can’t recall if Kitsune AS2 had any missing handlers, but regardless I don’t think it should cause your prompt issue. I suspect that the issue is client related, specifically with the interface or the catalogues.
I would say try using the legacy media server first, if it still doesn’t work then try using Houdini. Whatever works for you 