The biggest mish-mosh of temporal craziness was in the movie "Frequency". But in that case it was caused by a funky Aurora Borealis, which waxed and waned so that inconsistency wasn't a problem. I've said, in another thread, that it might be that the effects are governed by the method of time travel. Even in "Voyage Home" Spock said that things might be thrown off by the additional weight of the whales and water, so....................