Sounds like the ignition over ride is not the end default in the electrical wiring. But, it's wired correctly and here is why. Think of it this way, your engine is running and you need to exit the coach. The steps must be allowed to deploy for safe exit and entry.
Your issue is what you have discovered, a warped screen door, which breaks contact, thus signaling the system you are exiting the coach. There are two remedies; have the screen door fixed, or put an inline toggle switch near your exit point, to isolate the screen door contact switch(but have it fixed as well). The second one however, requires you to remember to activate the switch, to effect stair deployment.
Look at the bright side, you have learned, when people are waiving at you with funny looks, NOW you know somethings up! A lot of us in here learned that lesson i'm sure. Welcome to RVing, you will be a pro in no time.