As a slide fire owner, and one who has put it on several 15-22s...

I never installed their muzzle device. Keys to making it work, IMNSHO, are:
1) Make sure your bolt rides SMOOTHLY on the rails. This means that the rails have to be straight. Make sure everything is clean...
2) Use VERY LIGHT forward pressure. And I do mean light. Since this works off of recoil, the 22lr has to overcome the bolt and any forward pressure you put on the rifle.
3) Use good consistent ammo. I personally use CCI. You are relying on a consistent amount of recoil, and so the ammo needs to have a similar powder charge. some ammo is notorious for not being consistent.

Honestly, I had no issue the first time. Some people seem to get the hang of it.

I don't use the slide fire much. I don't care for the ergonomics, to include the butt stock. However, I break it out occasionally (especially on my 9mm suppressed SBR AR...), for new shooters to end their day with....