It’s the cause of numerous divorces and murders. Well, not really. But certainly intense frustration and perhaps a marital spat or two. You know all about it: that thing that happens when someone pushes the button to unlock the car at the exact same time someone pulls the handle to open a car door.

Everything gets stuck: the car won’t unlock, and the car door won’t open. Sometimes you have to run through the whole shmeggeggy a number of times (unlock, open door, but NOT AT THE SAME TIME!) until things mercifully get unstuck.

It’s something that happens to everyone at some time or another.

Now, Mental Floss, via Jalopnik, tells you exactly why this happens, for those of you who are mechanically inclined and searching for a reason—any reason—this happens. Because it’s so darned annoying. (And they even took apart a car door to show you how it works).

But the truth is, it’s really simple, the reason you can’t unlock the doors while opening them. The mechanisms are close but separate. When you try to activate them at the same time, they bump into each other with the result that both processes are blocked.

Doesn’t matter if your car is old or new. It’s still the same two processes. They can’t be used at the same time. Mental Floss suggests you think of it as not being able to breathe and swallow at the same time.