All babies should be placed on their backs to sleep until 12 monrhs. In realuty, when you have a 10 month old or a baby who is standing, it's hard to "place" a baby in a crib because they dive fire the crib and settle into any position they want. Which is why is important to have nothing in the crib they could suffocate on.
But a 6 month old is different. You are right, baby should be put in crib on back. Not on side, not on tummy. When your baby can roll over he will and then you don't worry so much. At this point, Back to Sleep is safest.
But so get rid of a swaddle or anything constricting his arms at this point. If/when he rolls over on his side or tummy he NEEDS his arms free to lift his head if he gets into trouble. A sleep sack is fine, a swaddle or anything keeping his arms tight is not at this age.

You don't trust her. There was something about an ER visit th ad to happened, and every day he takes 2 naps with the nanny, and you don't trust her. That's a lot of not trusting. Find a new nanny immediately.

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