Comment 41 for bug 1464917

I can confirm too that the issue is probably something to do with the swap usage.

My first guess was that the problem has something to do with the system's update, but seems that real cause is the swap usage. The shutdown usually goes fine when the system is used only for a short time and fails after a couple of hours of usage, when the system accumulates some data in the swap.

I did today some test and I got the following result:
~10 hours uptime (idle), 45 MB swap usage - the showdown went fine
~50 min uptime, 2.2 GB swap usage - the showdown hangs