They're not that unusual in aluminum, which has a talent for memorizing distortions. If the former, the bends will remain when the shrouds are slacked completely, and you might consider having a little conversation with the builder. If the stick straightens when the load is off, or if this is somehow a learned bend, it's tuning. The other tuning possibility is that, um, you' re doing a horrible job. Try starting from the bottom and working up, taking up a little at a time on each turnbuckle, and checking frequently to see that the mast is staying straight.
Some woods bend easier than others.
Let me know how it comes out. The mast is 2 years old, professionally built, sitka spruce and the builder faithfully followed the old masts dimensions. I have tried adjusting every way imaginable dozens of times in the last two years and have followed advice in various books including 'The Riggers Apprentice' Also the mast is a single spreader rig I have thought of adding jumpers. Strangely the boat sails fine under all points of sail, but, that S is driving me nuts. Oh, dear, a scoliotic spar.