Not sure why but on my Windows, some of the feathers you can't save at, (most notably the first one and one right at the start of chapter 4) and sometimes you have to confirm multiple times on the save button before it will save. So far it hasn't been much of an issue but I just died at the start of chapter 4 and will have to go through everything between my last save and the non-working save again.
Edit: what I mean by you can't save is that I just keep pressing save but it keeps making a click/no effect sound no matter how many times I press.