Sounds like the doors slightly warped. Try rubbing coloured chalk on the door latch then close the door then open again and look at the catch plate in the frame to see where the latch is catching [shown by chalk deposit]. Anther alternative is to gently push the door until it touches the catch plated then mark off the position of the latch see if it lines up with the gap in the catch plate if so the door hasn't dropped it's most likely slightly warped so the latch is not reaching the catchplate latch slot so the plate has to be moved. Or sometimes I've got away with taking the plate off and widening the gap with a file fitting the plate back in the same position.
