A few months back I replaced the original 3-way switches (one in the
house, the other in the garage) for our patio floodlights by 3-way
switches with pilot lights:
All was well while the original incandescent bulbs were still in place
(except that I was disappointed in the brightness of the pilot lights).
Now, after replacing the original incandescents by compact fluorescents,
the behavior of the pilot lights has changed:
Now the switch in the house has become an "illuminated switch" rather
than a "switch with pilot light." IOW, now instead of the light being
off when the outside lights are off and on when the outside lights are
on, it is on (and much brighter than before) when the outside lights are
off and off when the outside lights are on.
The one in the garage still behaves as it did before (i.e., on dimly
when the outside lights are on, off when the outside lights are off) if
the switch in the house is in one position, but when the switch in the
house is in the other position, the light in the switch in the garage
remains off no matter what position the switch in the garage is in --
even though it still switches the outside lights on and off.
I cannot even figure out how the switches could be constructed that
would cause either of them to behave this way.