"Use only one instance when started from file manager" does not work (xubuntu)

[Hampelmen]

System:
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XUbuntu 19.10
vlc 3.0.8 Vetinari

Problem:
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Even though the option is checked, vlc will always open a new instance.

Using "Allow only one instance" is no option, because the I cannot use another instance, when not started from file manager

What did I already try?
====================
- vlc --reset-config
- apt-get purge vlc; apt-get install vlc

[Rémi Denis-Courmont]

Probably because VLC cannot connect to the session bus.