TRESO's are very good, I have SlixShots on my Uberti Walker. They are stainless steel and are made for #10 Remington caps. The factory nipples on the reproduction guns are not the best, it is a common fault, and often times as you say, they don't seem to like #10 or #11 of some makers. Left picture is SlixShots, right picture with blue back ground is SlixShot, TERESO, and factory Italian nipple. I think I paid $40.00 for a set of six SlixShots for the Walker on Badman Bullets web site. See link below:
https://www.badmanbullets.com/OnlineStore/proddetail.php?prod=SliXshot-Black-Powder-Nipples
I think they are $36.00 for a set of six for the 1861 Navy Uberti. I got their SliX Driver tool as well, fits the nipples like a glove and seems plenty hard. My Uberti Walker with SliXShot nipples installed. Factory nipples sucked on the Walker as well. I think you may be able to get a set of the TRESO nipples for a bit less than the SliXShots. They are very good as well.
If you are new to shooting black powder percussion revolvers, here is a link that will tell you more than you want to know about nipples and caps. Turns out, caps aren't just "caps, is caps!" One manufacturers revolver might like a size #10 cap, another might prefer #11, and some factory nipples aren't all that great either. The CAD drawings of the different types of nipples and manufacturing differences is great in this article. It has great CAD's of the after market nipples compared to factory ones as well. Turns out all #10 caps or #11 caps are not even the same dimension from one manufacturer to another either.
Some of the Italian factory nipples are not consistent in size/length, although from reading this forum, I believe they have gotten better than they used to be. It is possible for one or two nipples to not (using the same size/brand percussion cap of course), seat to full depth, so that the cap can drag as you are trying to cock the hammer and rotate to the next chamber. You can check this easily, with the revolver unloaded, and just capped, shooting dry fire so to speak, just busting caps with each shot. Inexpensive way to try and figure it out. Safer too. If you find the nipples are at fault, flip side of that coin is what your getting, fail to fire, either nipple is short, or too fat in diameter, and cap isn't seating all the way down on the nipple rim, but is low enough it isn't dargging or locking the cylinder up.
Link to article on Nipples/cones/caps:
http://www.theopenrange.net/forum/index.php?topic=9093.0
Left SlixShot, Middle TRESO, Right factory Italian nipple.