Toto toilet dripping but can't find leak

I have a Toto toilet that makes intermittent dripping sounds that are driving me crazy. It sounds like it's coming from the bottom of the toilet, not somewhere in the tank, though there is no water build up anywhere outside the toilet. I did the food coloring test and the water isn't dripping into the bowl. Any advice on what this could be?

Does it happen more when it is windy outside? Does the toilet in question have the UniFit adapter? Air pressure in the vents can cause the water to rock in the bowl...some can slosh over the weir and down the drain. Also, after a fill, it may take it a few minutes to equalize the water level. This is more noticeable on the older version of the Unifit (the newer ones came with some sound insulation on them). If you shut the water supply off, does the noise stop?