I want to use an old board as a starting point for a new one; but the old one has a problem: length minimize doesn't work on the GND net. Other nets are OK; but I'm getting lots of GND rats needlessly crisscrossing the board after I ECO in the changes. The only way to get rid of them is to actually route GND pins. Anyone seen this? I have other designs that are not affected but I don't know what it is about this particular board.