Windows Live mail won’t download all messages

Over the last few months, Windows Live Mail has not been downloading all email messages. It will download most of them, except for one or two. These will stay on my IMAP server along with the others (none are deleted from the server) and I can see them on webmail. They also get downloaded to my iPhone no problem. I've missed some important emails this way so now have to double-check webmail or my phone regularly to make sure Live mail hasn't neglected to download something. There is no consistency in which emails are not downloaded. It's happened from at least four different recipients, all of whom I've received emails from into Live Mail successfully, sometimes on the same day as the ones that won't download. Is there anyway to make sure Live Mail downloads everything? Thanks.