"The little snail carries its own house."
Translation:Le petit escargot porte sa propre maison.
Because it means "own" and not "clean."
- sa propre maison = its own house
- sa maison propre = its clean house
Have you heard of fickle adjectives? Here's a good lesson on it, with lots of examples.
Which is why I don't usually approve of teaching "bangs" to beginners as they stick to it once they learn it, even when they become more advanced.
As far as placement is concerned, fickle adjectives are the most complicated it can get. Essentially, it all depends on the meaning of the word.