LO has BAD reflux and was in a nap nanny and swaddle. She learned how to roll so we knew it was time to transition her to inclined crib and unswaddle. She didn't sleep well at all in the nap nanny unswaddled and I was worried about her pushing herself out even with the harness on. We initally tried the one arm out swaddle and that went TERRIBLY. So we went all in on both arms out Thursday night. That night was rough.... she went back into her swaddle and nap nanny at 3am. But every night since then has been going better and now it even seems like she likes her freedom. She sure is all over the crib! So if you're trying one arm out and its not going well... maybe go ahead and try both arms out. For us, it seems like having one arm free and one arm tied down actually made her more upset. Good luck!