Ubuntu – Cannot open folders from icons on desktop

I'm on Ubuntu 18.04 and noticed sometime that I cannot open any folders from the icons on my desktop anymore. The following error is given in /var/log/syslog when trying:

$ cat /var/log/syslog | tail -3
Jan 16 17:59:51 drstoop-pc kernel: [  657.870793] [UFW BLOCK] IN=wlp112s0 OUT= MAC=01:00:5e:00:00:01:c4:71:54:33:0a:b0:08:00 SRC=192.168.0.1 DST=224.0.0.1 LEN=36 TOS=0x00 PREC=0x00 TTL=1 ID=0 DF PROTO=2 
Jan 16 18:00:33 drstoop-pc signal-desktop.desktop[4016]: {"name":"log","hostname":"drstoop-pc","pid":4016,"level":30,"msg":"Sending a keepalive message","time":"2019-01-16T16:00:33.885Z","v":0}
Jan 16 18:00:34 drstoop-pc nautilus-deskto[4026]: cannot open folder on desktop, freedesktop bus not ready

Nevertheless opening the desktop folders works from a nautilus window and also after killing and restarting nautilus-desktop. Restarting only helps till the next reboot:

$ killall nautilus-desktop
$ nautilus-desktop &

But I'd prefer a bug-fix, not a workaround… any ideas? THX!

Further logs

Kill, restarting and opening a folder from a desktop icon results in following /var/log/syslog:

Jan 16 18:09:48 drstoop-pc dbus-daemon[3099]: [session uid=1000 pid=3099] Activating service name='org.gnome.Nautilus' requested by ':1.21' (uid=1000 pid=3228 comm="/usr/bin/gnome-shell " label="unconfined")
Jan 16 18:09:48 drstoop-pc dbus-daemon[3099]: [session uid=1000 pid=3099] Successfully activated service 'org.gnome.Nautilus'
Jan 16 18:09:48 drstoop-pc dbus-daemon[1927]: [system] Activating via systemd: service name='org.freedesktop.hostname1' unit='dbus-org.freedesktop.hostname1.service' requested by ':1.106' (uid=1000 pid=6160 comm="/usr/bin/nautilus --gapplication-service " label="unconfined")
Jan 16 18:09:48 drstoop-pc systemd[1]: Starting Hostname Service...
Jan 16 18:09:48 drstoop-pc dbus-daemon[1927]: [system] Successfully activated service 'org.freedesktop.hostname1'
Jan 16 18:09:48 drstoop-pc systemd[1]: Started Hostname Service.