Pages () not always working on every article

Sometimes when I used the [code]<!--nextpage-->[/code] link it doesn’t split the pages.

Sometimes it does though.

Both I and other users are having issues where sometimes it just ignores the code, no matter how many times you put it in.

This seems to have happened in the last week, has there been an update? (I’ll admit to guiltily allowing all updates without actually checking them through)