postgresql f10 hangs on shutdown

[Michael Cronenworth]

PostgreSQL hangs on shutdown causing me to have to hit the hardware
reset switch. Has anyone dealt with this issue? This has been occuring
to me for a long time, but since I cannot find much evidence as to why
it happens I haven't created a bug report.

Evidence so far:
-Before shutdown I can manually stop PostgreSQL successfully, but if I
forget and perform a shutdown/restart, it hangs on stopping postgresql.
-The process must be running for at least multiple hours. 4-8 hours
seems to be long enough. Otherwise it will shutdown OK.
-I don't even have to use a database for it to get into this bad state.

The shutdown process turns off NetworkManager, then sshd, then
postgresql, so I am unable to SSH in or log in to diagnose this issue.
Any pointers would be appreciated.