The old saying comes into play he If it ain't broke, don't fix it. :-)
What you are seeing is the way that unit is supposed to work. I own a
CA-271 amp. The reason the light stays on is so you can tell which device
you will be taping from if you were to start taping something. That is
also why (on my unit anyway) the wording for Tape Monitor is in red while
the other device settings are white. I know how much of a pain it can be
having your head in a unit for what seems like ages just to find out you
didn't need to be.
Hope this helps.
Lawrence