We've discussed this problem several times in the Forum. If you scroll down the posts for two or three months you'll find references to lots of specific kits - and complaints about warped and/or ill-fitting parts come up pretty frequently.
Part of the problem, I think, is that so many of the sailing ship kits currently on the market are so old. Revell used to be the almost-undisputed leader in that phase of the hobby; the U.S. branch of the company hasn't released a genuinely new sailing ship kit since 1973. (That's more than half the company's life. Revell has been out of the sailing ship business longer than it was in it.) The most recent Airfix sailing ships date from the very early eighties, and I believe (though I might be mistaken about this) the last new Heller sailing ship was H.M.S. Victory, which was released in about 1978. The sailing ship line from Lindberg consists entirely of reissues. A few of them appeared originally under the Lindberg label in the sixties, but most are old Pyro kits from the early fifties. And so it goes. Many of the problems with poorly-fitting and warped parts probably stem from the age of the molds - and the fact that the manufacturers take so little interest in them.
Back in the seventies a Japanese company called Imai made a small range of sailing ship kits that were really nice. In conjunction with the hoopla over the 1976 "Tall Ships" race, Imai made a series of waterline sail training ships on 1/350 scale. They were simple kits, but generally well designed and reasonably accurate. Shortly thereafter Imai started releasing bigger sailing ship kits. They were on quite a few different scales, but generally between eighteen and thirty inches long. The range included the U.S.S. Susquehanna, the French auxiliary steam-powered ship of the line Napoleon, reconstructions of the Golden Hind and Santa Maria, the U.S.C.G.C. Eagle, the Cutty Sark, two enormous Japanese sail training ships, and several others that I've forgotten. If I had to give the title "best" to a range of sailing ship kits, this probably would be it. They were intended for relatively inexperienced modelers, but combined high-quality moldings, good fit, and better-than-reasonable accuracy. (Any plastic sailing ship kit is bound to have some weaknesses in that regard. Such things as blocks, deadeyes, and upper yards and masts just don't lend themselves to reproduction by injection molding. But Imai always approached those problems intelligently, and did a pretty good job of solving them.) I've said more than once in this Forum that the Imai 1/125 Cutty Sark is the most accurate rendition of that ship in kit form, plastic, wood, or otherwise. I can't recall that anybody's disagreed with me on that point.
Imai, unfortunately, went out of business about twenty years ago. Some (probably most, actually) of the Imai sailing ships have reappeared over the years under the labels of other manufacturers. Most of the 1/350 sail training ships are currently in the Academy catalog, and Aoshima recently has reissued the Cutty Sark, Napoleon, Susquehanna, and the Japanese training ships. (Some of the others may be available in Aoshima boxes too.) Unfortunately the Aoshima prices are pretty staggering. And I haven't seen the inside of any of the Aoshima boxes. The old Imai kits were notable for, among other things, their unusually thick, precisely-formed and beautifully fitting hull halves. Whether Aoshima has duplicated that technology I don't know.
Plastic sailing ship modelers (all 25 or 30 of us) are watching with great interest the behavior of the Russian manufacturer Zvezda. Most of its ship models so far have been re-releases of old Heller kits, but a month or two ago Zvezda released a 1/72 scale medieval cog. That one really excited me - first, because the appearance of any new plastic sailing ship kit is a rare event, and second, because a cog is such a fine project for newcomers to the hobby. I haven't seen the Zvezda cog in the flesh yet, but a couple of Forum members have reported that it's an excellent kit.
I'm afraid this is a pretty depressing post. There are a fair number of good kits out there. The very best of the Revell, Airfix, and Heller ranges are outstanding products. But that problem of aging molds does seem to be a real one.