Hello folks. In my bath/shower, when I flip the lever to open the
drain, it pops back up a bit which leaves the drain partially closed
and slows the flow of water down the drain. Any idea how to fix
this? I flipped it opened then closed a bunch of times hoping that
would fix it, but it didn't. It's a standard bath tub/shower,
installed in the late 70s.

Thanks for any suggestions.....

Mike