Make sure all mast wires have been "shaken" out so there are no "kinks"... I don't mean where a wire is crimped (but that would certainly cause a similar problem) rather that they aren't twisted or unable to lay flat. Check the connections to the mast for a somewhat flat attachment, one that doesn't look twisted under itself or "out of position"...i.e. natural looking...not tensioned. Do this inspection as you get the mast ready to elevate. Just one twisted wire will upset the proportional relationship. While the mast is on the boat on the trailer in position to be stepped, with mast end connectors smoothly fixed to the big shackle and lower ends disconnected, pull each wire so that it is untwisted and free from any other impediment and lay it out flat near its boat attachment. It should just lay there untwisted. Both sides should look the same. Most trailer sailors will leave their mast wires connected when putting the boat in travel position because it reduces set up/take down time in the parking lot. This is the common time when a shackle or wire can get twisted. And YES shroud adjusters will help prevent this occurrence and make your rigging process a bit easier. Good Luck...enjoy the boat.
...Oh, by the way. If you're still having problems with this issue, you can tie the forestay to the stem with a couple windings of small diameter line so you can still get the mast up and do some sailing. Sometimes. jury-rigging in such a way can help get the kinks out and perhaps clarify the problem.......... anyway, don't be surprised if that happens. Just know that the more you mess with the gear the greater the likelihood you'll get it sorted out.... that's my experience anyway.