If you have a door that isn't latching properly, a simple modification to the strike plate will almost always solve the problem. With just a few tools, some cardboard and a few minutes of time, you can fix this issue.
Step 1 - Remove the Strike Plate
Remove the top screw first, then the bottom. Place the screws and the strike plate in a safe area for later use.
Step 2 - Cut the Cardboard
Use the strike plate as a template and cut a few pieces of cardboard. The cardboard should be exactly the same size as the strike plate. The thicker the cardboard, the harder it may be to cut, but it could save you from having to use several pieces while packing it out.
Step 3 - Place the Cardboard
Place the cardboard behind the strike plate. Place the top screw in and tighten it slightly. Close the door and test the fit. If the latch is still sticking, you may need to add another piece of cardboard. Repeat the steps until the latch catches like it should.
Step 4 - Reinstall the Strike Plate
Once the latch is catching as it should, you can go ahead and tighten up both screws on the strike plate.