@Tervez Did you possible used XComUtil for the random UFO-Floorplans?
http://xcomutil.scotttjones.com/
One of XComUtil Feature is this:
Do you want to randomize alien ship floorplans before each battle? (N)
This forces a new ship floorplan to be generated before every battle. The
random seed is taken from the time of this battle, so that every design is
unique. Since this option is only necessary for people who have played
the game for a long time, the default is No.