New Toto Nexus is leaking through tank's mounting screw

Toto Nexus
Just got my nexus installed by general contractor, who subcontracted to his plumber. One screw that holds tank is leaking, and I am not capable to convince my contractor that plumber needs to do usual trick that I found on this website (sand fitting for the screw)…says that I need to get new tank and doesn't want to do any tricks as it will void warranty. I guess I will give Toto usa call, any advices what I should expect or do (besides shooting my contractor

How do you know that it's the screw that is causing the leak?

It's not a trick, it should be standard practice.
And there is no way, that making sure the surfaces are smooth could void a warranty.
The Nexus tank needs to be tightened down equally on both bolts.
A turn on this one, a turn on that one.
I would guess, that if he just removed the tank, and reset it, being very careful that both screws pulled down evenly, it would be fine.

By the way, I just picked up three of the Nexus toilets for stock.
They are frigging nice looking .
It's too bad we're not in your area, we would "Make it happen".

maybe not out of area?

I am in Sammamish, maybe it is close enough? How can I reach you?

I work in Sammamish all the time.
phone number is 206-949-5683