I just recently bought my first muzzleloader and got the traditions shedhorn and after first trip to the range I am running into a issue with my caps. I have the stainless #11 nipple installed and my RWS 1075 caps will not go off from the hammer reliably. I had some that took 5-10 hammer falls before the cap would go off. out of 20 caps that i tried maybe 3 fired first try. When the cap goes off the rifle shot fine. The caps are seated all the way on the nipple to the best of my ability. I question if it could just be bad batch of caps because it took 3 hits from a hammer to set one off on the concrete as well. anyone else have this same trouble with rws caps or is there something I am doing wrong?
any help would be great.

RWS are the only caps I and my wife use. Never had more than maybe 10-15 bad caps from them in 40 yrs of shooting black powder.
I have used Remington, CCI. and a few others, with much higher failure rates than RWS.
Traditions shedhorn usually come with nipples for musket caps? If this is the original nipple, then the mainspring may be a little weak.
Just in case that the geometry of hammer/nipple is off, try a different nipple, after you try a few new caps from a different batch.
If the problem keeps occurring, its probably the mainspring. If you have a friend with a caplock, try the problem caps on his lock.
Good Luck

Since the #11 nipple did not come with the rifle, I would suspect that it may somehow be different enough in dimension from the factory musket nipple that the hammer to nipple contact is not right.
Check that the hammer face makes contact with the nipple perfectly flat and square, you may need a taller or shorter #11 nipple.
I've had nothing but great experiences with RWS percussion caps, they are my cap of choice.
Have you tried it with the musket nipple and musket caps?
I know musket caps are hard to come by right now, I may have a few to spare that you could try if you can't find any.

Best nipples ever made were the Uncle Mikes Hotshot Stainless. Out of production now, but show up every so often on ebay.
My wife's rifle has one that has been there more than 30 years! 2 misfires in all that time...wish I could say that about my flintlock!
Kelvinator is right, if you changed out from the factory nipple, the geometry is not right for the hammer strike.

Track of the Wolf has Hot Shot nipples in 6-1mm, 6-.75mm, and 1/4-28.

The also list the dimensions of their other Nipples so if you need a slightly longer one you know what might fit.

https://www.trackofthewolf.com/List/Item.aspx/64/1
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I am gonna go out on a limb here, and suggest you buy this little doo-hickey call a mag-spark. It converts percussion caps to 209 primers

I use the RWS caps exclusively on all my muzzleloaders, and have never had a misfire, IF the bolt or hammer spring is hard enough to seat it all the way down on the priming compound. They are tougher construction than most others, and also tighter fit on the nipple. Usually the first strike seats it tightly, and the next sets it off. It is a true # 10.75 diameter, and others are looser and a # 11 diameter. CCI Mag caps perform just as well, and are a little larger to fit further down on the cone

I’ve used Remington #11 percussion caps on my T/C Hawken for over 40 years and have never had a misfire.

I love my T/C Hawken, and so do a lot of my hunting buddies. Seems like every year one of them is trying to con me out of it!

The T/C Hawken was my first muzzleloader. I've taken a lot of deer with it. I started off using CVA #11 caps but had too many misfires. Once i switched to the Remington caps i never had another misfire.