Not unheard of for smaller planes & cargo planes during loading/unloading if not done correctly.
So I guess it's theoretically possible depending on the load, the slope of the ground, plus if a significant amount of passengers are jammed at the rearmost door #5. Someone can do the calculations... You probably need > 55 % mac for a 747 to tip over.
A few years ago an airbridge failure at Malaga nudged a Sterling 737-800 door upwards and tipped over the plane. It doesn't take too much force...
https://www.youtube.com/watch?v=wj1xGUTcXT8