Have you tried sending a whole bunch of f(LF)s in a row? Maybe that's what it wants

Sorry, perhaps I wasn't clear. Yes, that's exactly what I'm doing. I'm sending f<LF> about 20 times per second. i.e. 40 characters per second. I've tried sending at half that speed, tried typing it manually in a terminal program and tried only sending it only once. I haven't tried sending it faster than 20 times per second, because I've discovered that overflowing the Empeg's buffer will crash it. (as I accidentally did with the volume command)