When a slip stitch is part of a decrease, always slip it knit wise. In what way is the yarn twisted...? Do yo mean the stitch? Maybe you're wrapping the yo/yfd wrong. The yarn should be wrapped around the needle the same way as you do for a knit or purl stitch, and you would always work into the leg closest to the tip of the needle for it to remain open. That leg could be in back or in front of the needle.
sue- knitting heretic