Hi Diane - I put two threads in each slot of the raddle of my Louet Jane loom making it 10 epi.

Hi Katherine - You have taken me back 15 years to an unexpectedly disastrous warp experience.
I decided to do a supplementary warp scarf and experiment first with cotton rather than use the silk that I had earmarked. That cotton was 'gifted' to me and was a mercerised crochet cotton encased in a plastic wrapping. I warped it up on a wooden warping board and contained the ball in a plastic container so that it didn't dance all around the joint.
I warped this front to back and didn't use a raddle as the reed and heddles were being used as the substitute.
Well the warp was as if it was a live worm! Twisting and writhing around like it was unable to find a resting position.
I persisted, got the warp on and the project came out really great.
Part of my figuring out what had occurred led me to some ideas and remedies - rightly or wrongly. I considered the 'S' or 'Z' twist in the yarn (which was a tightly woven y\thread). The remedy in this case included rewinding the ball of thread so that it became the opposite to the 'factory' ball. I also contained the ball in a cardboard box when I rewound it to minimise any static electricity from rattling around in the plastic. I was also particular as to how I chained the warp. Tried to eliminate any twist - but with my anatomy, I find this almost impossible in the main.
This made a huge difference to how the yarn behaved.
Fast forward to yesterday. The warp behaved badly. This time it was not nearly as bad as the previous experience. Probably only about 1/10th the disaster. But it did make me think.
I used the same yarn as I have been using for ages. Namely, 2/8 unmercerised cotton. Wound a 6 yard warp on a horizontal warping mill (not unusual - do it often). Chained it off as per usual. Warped back to front this time using a raddle. (This is only the second time that I have used this particular raddle). Frequently there were 4 threads to a slot.
Whilst winding on the chain was showing a profound twist which I was having to take out. The threads coming out of the chain weren't so much twisting - but rather the chain itself was twisting. If I lengthened the distance between the chain and the raddle the threads started to be rather 'dynamic' until controlled with more tension.
Finished winding on and instead of lifting the threads out of the raddle and dropping them down, I pulled the threads through the raddle to drop them down. Viola! the threads contorted somewhat and twisted round themselves into a somewhat controlled tangle.
What was different? Conclusion - my chaining could have introduced some more twist than I usually do. But the main difference was the raddle. It is made of plastic and I had more threads than regular within the slots so that everything rubbed together creating a friction. I had also wound the warp onto the back beam rather quickly which meant that these threads were moving through the raddle slots a bit quicker than usual.
I am not telling you this to suggest an answer to your particular experience. More probably just saying that "there is more to heaven and earth Horatio". Maybe just some moral support for your predicament.
But I know that pondering and small changes might help give you renewed confidence in that pesky yarn.
Perhaps give rewinding the ball a go to change the fibre direction. Can't hurt.

Hi Mary - the Harrisville Shetland wool that Jane sells and we use for weaving is a 2 ply yarn - not a 1 ply knitting yarn. Harrisville uses the name "Shetland" to identify "the size of the yarn and not the fiber content".

Hi Mary
Yes you are right that the Donegal yarn I was having problems with is single ply. I got on to the manufacturers at donegalyarns.com and they put me in touch with a weaver called Brenda Hewitt in Falcarragh, Co. Donegal who uses it extensively for both warp and weft in her weaving and manages fine it seems. It is definitely sold as suitable for weaving anyway. For the time being, I think I may just use it for weft yarn, and have ordered some fine 2-ply yarn called Zephir from a company called Artifilum in France which I hope will be suitable. On the subject of creating twist during chaining, I think it might be much easier to avoid this if I was using a warping mill, as I would not have to negotiate the change of direction moving around the pegs on the warping frame, when it seems almost impossible not to twist the yarn!