I just returned from my URC dealer, who is a real
pleasure to work with. The upshot for the moment
is that he wants his installers to have a look at it.
I think it is just great that the same installer who
did the MX-900 programming in 2007 is still there
and has the original mxg file, so he can download
it to the remote and really see that the behavior
changed. The symptom he will use is that the
ON button now flashes "macro" for about 20 seconds,
which it did not do during the four years
before I re-downloaded the mxg file three days ago.

It's also great that URC is still making and selling these
remotes, because they are wonderful devices. One option
my dealer offered me is to buy a replacement (with warranty)
for $224 (I paid $320 plus installer time in 2007), sending in
my present remote. I would have got the new remote immediately
because they had them in stock. I got to see one and it looked
identical to mine, and the keys seem much improved! In any case,
they now give a satisfying click when pressed. So I will definitely
consider getting a replacement if we can't figure out what is
wrong with mine.

My dealer has experience with dozens of MX-900s, still recommends
and sells them frequently. He has seen problems with the keypad
membrane, but never such a problem as I am having. Another
symptom I found last night is that the volume up button repeats
itself many times with one push. I was only able to stop the volume
increasing by pushing the volume down button, which then also
repeated many times, turning the volume off.