mpv mpris doesn't work correctly in flatpak

[MinmoTech]

I'm currently trying to switch to the mpv flatpak, but mpris is currently not working correctly when using 3 or more instances of mpv.

The reason for this is that the process ids are in their own namespace and therefore start with 1 again.

The 1. mpv proccess takes the dbus identifier "mpv", the second and subsequent instances try to take "mpv.instance2", which causes a conflict from the third instance on.

Could this plugin include a check for further conflicts or otherwise circumvent this problem (appending a random number maybe)?

Thank you! :)