"da_door_fl_10" is a macro (sub-object, if you will) of a door element. You don't use it, your doors do.
It's having an error due to 1) A setting you made in one or more doors and 2) Graphisoft's failure to handle that setting gracefully.
The most common cause of 'Polygon degenerated' is setting the width of something (a casing or frame, for example) to zero in an attempt to turn it off. AC tries to build what should be a rectangle, but one dimension of the rectangle is zero so it collapses on itself and reports an error.
Programming-quality-control-wise, there's no excuse for this. The door object's code should catch such errors and decide not to build the collapsed thing. It is properly termed a bug.
But, even though it isn't your fault, you'll probably fix it before they do, by finding that zero setting. Set it to very very tiny instead, or look for a switch to turn it off another way. Unfortunately this error doesn't give the ID of the bad guy so you have find it the hard way. Notice which sections give the report; the door is in those.
I glanced at the code for that macro in hopes I could determine what piece of the door it was making, but the part is badly commented and it's hard to say.
Good Luck,
