Caps are one area where it's a matter of trying them to see if they'll work for you. For example, I've never had good luck with CCI caps on most of my guns. I get too many misfires. I've never had any problems at all with Remington so that's what I use almost exclusively now. On the other hand, you'll see just as many people who have no problems at all with CCI but have problems with Remington, etc.
I'm not sure what causes this. If it was a problem on a single gun, I'd suspect the way the cap fits the nipple, but a lot of us have those results with different guns and different brands of nipples. I'd suggest getting a can of every brand you can find and going shooting. If something isn't going to work for you, you'll know it soon enough. If none of them work well, then it's time to consider a different brand of nipple, or filing the nipple to fit the cap a bit better.
I've heard nothing but good about RWS caps but they're hard to find in some areas.