listener referring to session box track from modifier update issue

Hey,

I want to receive the volume value from the 1st track of my session box.
So I set up a modifier for that session box track number and a reaction with a listener to this track's volume:

self.song().visible_tracks[self.get_modifier_value("m1")].mixer_device.volume.add_value_listener

Problem is: the listener apparently does not get updated after(!) the modifier was updatet.
So I only get the volume of the current track, when I move the previous(!) tracks volume.

When I then move the session box to another scene (not changing the track) it works!
(I guess because the modifier was updated without changing the number, so the previous track is the same track now...)

Did I miss something? Is there a simple workaround? Or can this be fixed?
Thanks