A.I. Transport issue

In a few games that i've played, i have an alliance going with one of the a.i's and we are attacking another a.i. That A.I. gives up to a minor race. Somehow we have both sent transports to the same planet. If mine arrives first it seems the a.i doesn't check for the current owner (or new owner if i've just taken it during my part of the turn) The A.I. invades and we go from being allies to at war without breaking the alliance. Any bod else get hit with this issue?