Best guess: you have a very tight cylinder gap and/or used some very "dirty" ammo whose powder burned into large-grain soot. Either way, or via some combination, crud built up at the back of the barrel and front of the cylinder.
This isn't necessarily a crisis.
With a snubbie you want a small gap, that way you get "max performance" out of 38Spl/38+P from a 2" barrel. The downside is that you need to wipe down the aforementioned areas more often.
My gun needs a wipe every 40 to 50 rounds. I consider this a very tolerable tradeoff for maximum velocity, esp. since my defensive loads are always high quality and tend to produce less soot. Ain't no way I'm going to end up shooting 40+ rounds in a gunfight!!!
So. Clean it in those areas, see if that helps. If it does, do the "revolver checkout procedure" and see what the barrel-to-cylinder gap looks like. If it's real narrow but the gun can go at least 30+ rounds between wipes (not full cleanings here, just a quick wipedown) then in my opinion shrug and go on.
If that gap is REAL tight it needs fixing. Now, you can send it to the factory but they're liable to open it up past optimum - .007" or more is "in spec" but nothing I'd want, again, esp. in a snubbie. The other option: take a flat fine knife sharpening stone and slowly and carefully file the back of the barrel to open the gap. Just a little will do and keep even pressure over the whole circle! This will let you set it up perfect.
What else...very cheap ammo (or esp. black powder "cowboy loads"!) will produce larger-grain soot, requiring a bigger gap. Cowboy action shooters competing in black powder categories often run monster gaps but the effect can be seen in some modern loads/powders...very VERY seldom in high quality defensive rounds though, you see that in cheap practice fodder.
If it's NOT "soot buildup in the gap" then something else is going on. This is just the first thing to look at and the most likely.
