If you have a bowpress you can let off the poundage, twist the string in the opposite direction, half a turn at a time till it is right; or let some weight off and move one strand from one side of the peep and bring it over to the other.Looking at the string in the usual way, if you move a strand from the right, infront of the peep and over to the left,the peep will rotate a little the opposite way.
Has your D-loop become loose? or have you altered something else?
If it is a small twist then sliding the two bits of serving that hold the peep in place will twist the peep. Assuming you have one above and below and the peep isn't served around the body.
I would be just as interested in working out why the peep has suddenly twisted as to fixing it.
One issue we find with Wendy is that the d-loop will eventually wear through the centre serving and the first sign of this is peep rotation. A quick replacement of the centre serving and fitting a new d-loop resolves it.
I dont have anexplanation aards do that for me but when I had new string and cables put on mypeep did the same eventually it was something to do with the serving on the ends or middle that were going the wrong way and also shooting a lot while string/cables set in.