This can happen if you’re syncing with iCloud and have one or more devices that don’t have the latest version installed. Unfortunately older versions get confused by a delivery type they don’t recognize, remove the link because they weren’t expecting it to have one, and then sync that change back out to your other devices. Once all of your devices are up to date, you can add the links back, and this shouldn’t happen again. We’ve also made some changes to help ensure this type of thing doesn’t happen in the future.