In further experimenting with my pop up rod problem, I noticed when I
force down the plug in the basin to make a tight fit, the rod comes up
as it should. In that sequence all is fine....but the minute after I
fill the basin with water and let go of that plug, the rod slides down
a little enough to start a slow drain. I checked the nut below the
sink to see if its loose. Its as tight as ever...so what would make
that rod slide just enough to start draining on its own?