Shamefully, I have one paywalled Nature paper. We all agreed in advance that we would make it open access (I'm not 1st author). Come publication day, I notice that it's not open access. 1st author checks with editor. Editor says it's "too late" to make it open access now that it's been published, even if it was published paywalled by mistake. These people still live in 1924. (we put the paper on Arxiv.)
villares