The sticking door latch thing just happened to me yesterday. After climbing through an unlocked window, I was able to open the door from the inside. I sprayed silicone lubricant in all the available openings, and it now seems to work OK. If you have an access panel on the inside of the door, remove the screws holding it and then spray lubricant on all moving parts. My door has carpeting glued on the inside, so removing it to get to the access panel is a bigger job. I will do that if it occurs again. Hope this helps.
Larry