Warm on top, cool on the faceplate. Never hot as far as I can recall with mine when I owned it. I would probably have it checked out.
I owned several of these but I don't have one right now. I do recall however, that the entire chassis is the heat sink and does get pretty warm as a result. I also seem to remember that my volume control did that same thing once.
Why don't you call JRDG and ask them? It's a more reliable information source than any of us.