The NW60-SP5-Box (with some important additional fixes after
SP5) abended.

I will try to attach the abend-log.

When trying to restart the server the following message was
thrown to the console:

NWSA.NSS cannot be unloaded because the following APIs are
still in progress: NCP 66

I had some abends during my life, but such a message is new
to me.

Does anybody have an idea what went wrong on that server?