I've seen warpage in 16mm and 8mm films that I've worked with. It's a pain in the neck without an easy solution.

First, shrinkage actually means shrinkage... meaning that simply pressing the film flat won't solve the problems of the sprocket holes no longer aligning with the sprockets. This is fairly rare but I saw it once in an older Chinese film.

Second, warping causes the distance between the surface of the film and the camera to change as the film plays, meaning that it is difficult to keep it in focus. This is more common.

If the shrinkage isn't too bad, someone could probably jerry-rig some glass plate method of keeping the film flat to counteract the warping. But it would risk scratching the film in the process. A normal gate tries to hold down the film at the edges... the tradeoff of a more closed in gate would be to crop more of the edges. My workprinter has an enlarged gate which captures more of the frame but also makes it less successful with films with slight warpage. Some of the home movies I've worked with have had this problem, and I've sometimes gotten around it by just trying various projectors until I found the one that was the best match for the filmstock.