The bees sometimes have problems with plastic, sounds like your other hive is doing better with it. If the bees cell size is bigger than the foundation imprint, then this can cause the same problem as well.
If the other hive has some other frames started but not layed up with eggs yet, you may want to use some of that to get the retarded hive started. One other thing that can help is to brush melted beeswax(if you have any) on to the plastic foundation (even though it may already be coated).
Contrary to popular belief, bees don't create straight perfect combs. Although some bees do better than others, and some do a lot worse.