The die just might not size far enough down the case to make it come out playing nice with the gauge.
I'd adjust the die to get the shoulder bump I'm after, period, and then just view/use the gauge as a QC check to make sure cases are coming out consistent.
The gauge is just a cookie-cutter gauge, so, arguably, you shouldn't even worry about cases fitting perfectly into it as long as the rounds work in your gun and every case comes out the same. It's more important that you get the desired bump you want and it works in the gun. Bumping more than you need to, just to achieve fitting into some gauge (instead of your chamber), seems dumb, as it will only lead to shorter brass life with more case stretch and a greater risk of a kaboom if you're pushing them hard.
(FWIW, I hate the mystery of cam-over presses and prefer presses/dies that have a full-stop and no mystery.)