I am not sure if there is an adjustable pelllet stop made, though I have heard my friends mentioning one. I had to make my own from a suitable piece of brass and hand filed it to the correct shape and size for the pellets I use.
Man, I wish you where in driving distance, I played with those a lot years back and I had it down but I would need to have a gun in my hands now to work on it,.....I think I have one of those pellet stoppers still around, if you need one let me know and I send out a search party to see if I find it
I broke mine also some years back. When I made a new one I also milled a hole in the side of the receiver so now I can adjust it from the outside. Much much easier.
I adjust it with the muzzle pointing down and get it so the skirt is just flush with the shuttle so it does not catch on the receiver frame. I have on occasion had to modify the stop or make a new one adjusting the ANGLE of the stop nose (the "L" part) where the pellet rides. The pellet rides that nose as it travels across. If the nose angle forces the pellet to "back up" as the shuttle begins to travel the skirt may catch the frame or increase friction against the next pellet. If it angles off too quick the next pellet may advance too far forward instead of disengaging. Hope that is clear as mud. In other words your new stop may not be shaped like the one that broke.
Here's a photo of an adjustable pellet stop, in this case set to shoot CPUMs.
I just got a new to me career in and had to adjust the pellet stop or shuttle when I put it back together would not feed ,I changed the screws on scope rail long in front short in rear now it works, Do not over tighten the screws or they will strip. and if you put the mag in with receiver cover off you will be looking for the magazine spring.
.20 caliber carbine with soft case 4 mags and fill probe.
I set my pellet stop for the 23 grain Korean pellets, I have about 30 tins.