"Well... I know back in the day the system wasn't as smooth as it is now. Souls got stuck in the World of the Living if there were strong ties binding them. There were also more people dabbling in forbidden arts to do lots of trapping. Truthfully, the "stuck" problem boils down to either crappy shinigami not guiding the dead to Meifu or your regrets are too strong to release your soul. As far as papers go, that's on the judges and other clerks to sort out your transgressions and soul quality, but still, you have to stay in Meifu until your soul can be released. I know people that have such strong regrets from life that they are giving the chance to walk in the World of the Living to resolve them, but that doesn't always help."

You are looking at one Gan Ning, but he won't admit it till he's sure you won't kick the can for knowing.