Prop physics go flying?

I have placed a number of prop_physics around my map, and for the most part, when I run the map all of my prop physics end up in a cluttered mess, as if you went in and ♥♥♥♥ed ♥♥♥♥ up with the gravity gun. For example, whenever I have a table with stuff on it in the finished map the table is lying sideways on the floor and all of the stuff on the table is scattered along the floor as well. Can anyone tell me why this might be happening? Thanks.

Prop physics go flying?