Old American Standard toilet from around 1954. Has some Fluidmaster
components in it.

It works OK but about 4 times/day it pumps maybe an additional gallon
of water in, so it has a slow leak.

I checked the stopper and it's apertu both look fine, but I spread
a little vaseline on both to help insure seal. No help. Overflow tube,
etc look OK.

Visual inspection looks OK but it leaks. Any ideas?

Thx,
Willie