Usually a twisted tippet is caused by large bushy flies that catch a lot of resistance in the air during false casts and twist a lot before landing. Large dry flies with large posts or wings can cause this. Large leeches and woolly buggers can also do the same thing.
Not adjusting the timing of your cast while casting these large flies can mess with your tippet. Remember that larger flies are more wind resistant and take more energy to move, and you will have to adjust your timing to wait for them to catch up with your line before starting the opposite casting motion. Do it too soon and you will get wind knots or twisted leaders. HTH a little.