Sometimes its offsync and sometimes its not. It look like the actors dont have a script at the time and just move theyr lips, and theyre dubbing it afterwards. Cuz even if its offsync theyre lips dont match what theyre saying..
I think the dubbing is just that bad. I mean look at the rest of the film. It looks like it was done on a used 3/4" studio cam from the 80's and the set pices are salvaged junk. I'm willing to bet that when they sat down to dub in english, the had nothing but used or borrowed equipment to lay the tracks with and they didnt really know how to do it. That was the end result. I happen to love it. It goes great with the rest of the film. I think that if they had got it right, a lot of the campy cheapness would have been lost.
The dubbing is horrible, and it is so intentionally. Not because of lousy equipment (although that could be a reason to why it's so bad if they had the intention of making a good dubbing) but intentionally. As you say, it perfectly fits in and perhaps also helps to found the basis of the overall appearance of the movie.