Faulty Chair?

In our office we have these nice adjustable chairs with a pretty wide wheel base at the bottom, so they are very stable. Stable enough that you should be able to fall asleep in them without falling out (Don't ask how I know). Apparently that is not stable enough for Martin. This morning he went to get out of his seat and while pushing away from his desk the back wheel got caught on a pen ( or cord?) and his chair flipped over with him still in it.

We've try to recreate the incident, but can't seem to figure it out.... Don't worry, Martin was not injured.

Also worthy of note, Martin was running late to work this morning, so he hurriedly tried to get dressed while working his way towards the door. He started to put on his hooded sweatshirt as he was going down the stairs only to find that he was putting it on backwards. Naturally, with a hooded sweatshirt on backwards one cannot see where they are going. Thus, Martin ran smack into the wall. Again.... Don't worry, Martin was not hurt.