Toto Drake II -- perplexed by leak

I have a Toto Drake II (new install) where water is very slowly leaking between the tank and the bowl and I cannot figure out how this is occuring.

After discovering the leak I detached the tank, filled with water and food coloring and let it stand over a bucket to see if water was seeping from the tank bolts, fill valve or flush valve -- no leaking that I could detect. I cinched down the flush valve a bit before this leak test as well.

When I installed the tank, I did so as evenly as possible -- the tank is touching the bowl in the three locations indicated in the installation instructions. The rubber gasket that fits over the end of the flush valve is oriented correctly and the tank is level and centered over the bowl.

Is it possible that the toilet bowl opening is out of spec enough so that the gasket between the tank and bowl does not fully seal? The gasket is new.

Any ideas?

Normally snugging the large nut does it.

If you have pliers, it wouldn't hurt to pull the flush valve and sand the inside of the tank where the parts fit in.

https://terrylove.com/forums/showth...oto-Drake-CST744-or-CST454CEFG-2-piece-toilet

I've already snugged the flush valve (did not sand). The really strange thing is that the leak does not seem to be coming from the tank -- at least no visible food-colored water is leaking that I can detect.

How sensitive is the tank-to-bowl connection? The tank is snug to the bowl at the 3 points of contact shown in the instructions. Any tighter and I fear breaking the tank.

The tank to bowl connection works fine.

I would look at the tank to bowl bolts. I would pull and sand where those go.