As for the original issue, it sounds like a simple binding that's going on, of which theres a few ways to deal with it.. One being simply hunt down the area of the pushrod that's binding, usually it at one end or the other of the outer tube exits, especially if you have relatively straight shot through the fuse. I've used a little graphite or silicone(wd40) in this area, and even put a very thin coat on the wire itself, that lends nicely to a very smooth assembly. As its only a plastic tube, with a solid inner wire, there won't be alot there to figure out...and...

I used Sullivan NyRods for quite a while, I found them extremely flexy, and needing more support to stay true then other set-ups. On the operation of them.. the "pull" side(when they're pulling) is reasonable, and I don't think there's any stretch going on.. but getting them to "push" a given surface is another story, and they tend to buckle and give more then a solid wire would.. and I think with these anomalys' it really doesn't make this hardware the best for any given set-up where you need rigidity and strength.

When the NyRod type of system is combined with a solid wire though it seems much more durable, stiff, and the control surface is very sturdy, with little chance of blow-back, which is the whole idea behind whatever system you use.... none of them are any good if you can simply and easily move those surfaces against the servo rotation.......

I use the solid wire inside, and cut what I'll call "bushings" and tack them to innerwire, the bushings are about 1/2" and I space them about 8"+ or so... this seems to keep everything solid, with less drag/binding, while still taking advantage of the easier installation of this type of rod system.

I've seen it both ways, with and without a bushed center rod, and I've used the plastic center rod, but overall I prefer a metal rod in a plastic guide.. it seems more precise for aerobatic applications.. that's for sure.