I had a problem with my dryer - can't tell if it's exactly what is
described here, but the symptom was continual beeping and it *really*
wanted to run in the cotton/high heat mode.

I found through experimenting that I could push (and hold) one of the
other mode buttons below Cotton and press the start button while
holding the mode button and it would successfully complete a cycle in
that mode (while beeping). I used the dryer this way a few times, but
I unplugged the front panel wires so that I wouldn't go crazy with the
beeping.

The solution was to have the front (button) panel replaced. My guess
is that the design is flawed and one of the buttons gets "stuck" after
a while. Odd thing is the diagnostics don't show a button stuck, so
it's probably just a partial contact - but enough to be detected as a
stuck button by the control board. Notice that with a working dryer,
you can push and hold the Cotton button and get exactly the same
symptoms.

Good luck,
Lance