I just saw something on this in the Sage Portal - does not talk about the cause but mentions some fixes (DFDM type stuff). I can't find the article in the Sage KB at the moment but here's what I copied - https://www.evernote.com/shard/s270/sh/8a55fa77-3c6c-4bc1-b135-f1dae3b07666/702efb311704084a56db10328d71ffb7