Actually, I seem to remember seeing this problem a few years ago, as I recall it was not the IRF-6 it was an intermittently sticky button on the remote. When the red light stays stuck on, do the all of 6 green leds on the side of the IRF-6 stay on also?

When this happens, take the battery off the remote while watching the lights on the IRF-6, if they go off you probably have a sticky button. You can easily fix this by cleaning the contact points very gently with a q-tip with a little alcohol on it, (take the battery off first) or you can get a new button membrane sheet these were readily available last time I checked and they were not expensive.

Sorry I did not think of this before.