In the stock there is a way to adjust for light loads mine seems to only work with 3 inch magnums none of the light loads I tried have worked.
My sx3 has never jammed. My wife's sx4 occasionally did in the cold only the first 200 shots. Nothing since or in warmer Temps.
I take every new semi auto apart, clean all of the old oil or grease off of the mechanism, and put a touch of symthetic oil on all bolt surfaces where there is metal to metal contact, and then manually cycle the bolt a few dozen times. This pretty much eliminates any of the new gun issues that some people notice. Other people just install the barrel and shoot, and they sometimes experience some issues for the first 50-100 rounds.
Can't speak to the SX4 but the internals and gas system are identical to the Browning Silver and Winchester SX3 and I've owned both of them and they cycled every target load I have ever run through them without flaw. The Maxus seems to be the exact same gas system as well and my Maxus SC cycles them all including the Rio Evo 24 gram (7/8oz) training target loads flawlessly.