It does sound like there is an issue with the spring inside the connector. Usually you can get them to seat better if you gently push in the poppet and wiggle it around to get the top gasket to engage more evenly. If there is ever damage to the gasket on top of the poppet or the bottom feet that hold it in place then you would need to replace the poppet with a new one.

The Sanke adapter actually has both beer and gas on it - it is an adapter that will allow you to put homebrew ball lock gear on a Sanke keg. But the beer connection and gas connection are different as well. The gas side has a notch or etched line on it that the beer side doesn't have. Really the physical connection is the same but it lets you know which side has the long dip tube. Also on the adapter it is easy since the beer is on top and the gas is on the side.

It is hard to tell just by looking but they are slightly different sizes. The beer side is slightly bigger so you won't accidentally put your gas fitting on the beer post and flood your regulator with beer. However if you push hard enough it can still happen so be careful.

There is a small ramp below the gasket that the balls ride across. One adapter has a larger ramp than the other B for big ramp b for beer.

The beer side has a bit if a flare before the indent for the ball lock. The gas side will have a ring at the indents for your wrench.

the gas has a thin line around the top of the bottom most portion near where the straight cuts are for tightening.