Reasons why labor does not post

We have just come across an issue raised by Finance where the GL does not match the Work In Process Report (you know, the only WIP menu that lists all words rather than WIP). Turns out some our labor entries did not post. There was no review journal. All jobs have been in balance. MES looked fine on some of the most likely problem users. Setting the Capture to Post Outdated Transactions but just wondering what people have seen as causes for labor not posting.