OK, hopefully you didn't just play around. The screws are used to balance the spring tension so both sides open somewhat evenly. Tightening a screw will in theory bring an arm out, loosening in. Don't try to do it all from one side, tighten/loosen as needed form both sides.

If that doesn't work, you need to look at other issues. If one arm stays stuck then pops out suddenly, it could be that a worn brake shoe is overhanging the bottom of the rim and getting stuck there (this is likely if they've been OK for a long time and started acting up suddenly).

Or there may be rust or dirt on the post, ading friction to one arm or the other. You may not need to take the arm off, add a drop of light oil (possibly thinned with solvent so it penetrates faster) to the front and back of the arms and let it soak in, then pump the brakes a few time and see if it improves.

Also, sometimes the brake cable is too long or short and tugs or pushes the entire brake unit to one side. The springs aren't strong enough to overcome this. This is most likely if the problem started after a new cable was installed.

That's for starters.