We've had a Toto Ultramax w/soft close seat for about a year. Seat was a bit unexpected in shape, but no problems. This week we installed our new Toto Drake in our kids' bathroom, also w/soft close seat. I had noticed the few times I tried it that the seat back seemed to "slap" back sharply against the tank when I stood up. At first I just assumed I had somehow leaned back against it, but today upon further investigation I found that isn't the case. If you press on the back of the seat near where it attaches, it seems to flex down a bit, and in doing so the seat back leans forward. When you stop pressing (or when in in use--you stand up!) the seat back is no longer being pressed forward from below so it relaxes back and hits the tank.

The seat on the Ultramax looks identical in every way, but does not do this! In looking at them they seem identical, and I cannot get where this small degree of flexibility is coming from. It looks properly attached and secure. Could it be warped underneath somehow? This is a small annoyance to be sure, but it IS a bit annoying to have this loud sharp sound in your ear each time. Any ideas? Anyone else seen this issue? Thanks-