The rear door is most likely a worn hammer on the mechanism. Take the handle off (single screw on endge of door) and you'll see a plastic hammer, which always wears out/misaligns, try just unwinding it further to see if this fixes it. If not I used a washer on the hammer to increase the area it acts on, which worked fine!
The front door has probably dropped slightly on its hinges, when you open it does it sag down slightly? If so the door needs rehanging, which is a bit of a tricky job to get right, or you can use my bodge involving a plank of wood and a trolley jack, and some gentle "tweaking"

If it hasnt sagged my next guess would be a sticky latch mechanism, try oiling it up see if it makes any difference.