The way I've found to avoid this is to hold the cylinder perfectly vertical and make sure it's full open before pressing the ejector rod. In other words, the extractor serves more as a guide and nudge to get them to fall free - not as an instrument for pushing them completly free of the cylinder. .357 shells should clear the grip just fine before the extractor is fully depressd
If the shells are stuck in the cylinders, perhaps running a brush through them every 20 or so rounds will help. I find this to be more of an issue when I mix .38's and .357's. I've also got a .22 SP101 and use the same technique. They never stick, and .22's are notorious for swelling in the cylinders.
If the shells are so swollen in a clean cylinder that they need to be forced all the way out - perhaps an ammo brand change is in order.
Since the ejector set up is not a solid piece on the SP101, there is going to be some play when fully extended. Don't know I would call it a design defect - but it is an idiocyncrosy of the piece.