[Shane@DBPerformance]

Bad return lines can cause that to happen. You won't see it much on DSMs, since a lot of people use hard return lines and your choice of return location is already setup. On other cars though, you always see people putting the return location on the pan below the oil level or having a crimped rubber oil return line or one that drops down too far and comes back up. When the return line is bad, oil can't return to the pan quick enough(it isn't under pressure on the return, gravity has to do all the work), so oil starts backing up in the center cartridge. If you let it do that for too long, then the seal will blow for good.