I am using a Grandstream GXP2140. When I am having an active call and another person is

calling me then I can switch between the two calls. The person set to hold should hear

the hold music but it only plays the beginning and then just comes silence. I don't get any error messages.

How can I set it up that it keeps playing the music?

Log:
2015-04-23 21:19:00.154957 [DEBUG] switch_channel.c:1961 (sofia/internal/sip:13@10.0.200.13:5060) Callstate Change HELD -> UNHELD
2015-04-23 21:19:00.154957 [DEBUG] switch_core_io.c:1026 (sofia/internal/sip:13@10.0.200.13:5060) Callstate Change UNHELD -> ACTIVE
 

Dialplan:
<action application="bridge_export" data="hold_music=$${sounds_dir}/music/song.mp3"/>

Thank you