Unicender - twisting rope?

I finally ponied up and got a unicender. Nice device - got the walker setup working well.
Now for my question.
It was too tight for my vortex so I switched to velocity and it fed nicely... Until I came down. I got more twists and turns than I ever have. I actually needed to hold the rope firm as it fed into the unicender to keep from making a giant candy cane. Found this srt and switched to drt to have less force on it. Didn't seem to help much. I am using the 'pull to go' or whatever you call it where you loop the rope over the handles and pull to squeeze them together.
I don't recall hearing this is a problem and in a quick search nothing came up that seemed to be the same- could have just missed it though. This isn't complicated - what did I screw up? Thanks.

I've only climbed on one once, didn't have twisting problems. But that may be because I had enough rope in play that my 150' rope was able to untwist as I descended. Generally it's a good idea to keep the tail of your rope free to allow it to release twist as a hitch or device generates it. Of course you can't always do that. It also maybe that your rope had some twist already in it and the Unicender amplified it. How do you store your rope? If you coil it then you're keeping or adding twist ito the line. If you flake it into a bag you can reduce twist every time you handle the rope. I use simple/cheap stuff sacks for my rope bags.
-AJ

Thanks Moss
My ropes just go in a bag or on a tarp. I have had some twists before from the hitches and usually unwind them afterwards - so I don't think there was much twist left over. I also believe this because I have twice as much as when using the distel. In the past that rope was used primarily for rads.
My theory - running the rope over the top handle gives two sharp bends. Since the rope isn't really round the handle edges are 'grabbing' the fibers of the rope which are angled in one direction.
Theory two - cover if rope may be looser and bunch up a little at the handle which could cause the same as above.
There has to be a simple answer as nobody else has this issue.