I have router table with a Bosch router.  The most bizarre thing is when I need to change bits.  The smaller wrench that holds the router fits perfectly when I put it on the router one way.  If I turn it over it only goes on roughly ½ way.  The router in that area doesn't have a nut, the hollow shaft simply has 2 flat spots on which to place the wrench.

This is a simple wrench made of cast steel.  No protuberances or anything that looks different from one jaw to the other.  I can maybe get a few pictures later today.

It doesn't matter which way I turn the router.