When you build soil enhancement/habitat/terraform on a planet the PQ level is not adjuting to the new amount of useable tiles.
eg playing Yor you build soil enhancement and habitat thingy on Iconia. Iconia's original PQ is 10 after buliding the soil and habitat the new PQ level should be 12. However due to the bug it remains at 10. This happens to all planets and seemingly all races.
I thought stardock had previously fixed this bug, ethier they havn't or its reared its ugly head again.