app_meetme.c: Unable to write frame to channel SIP/

After reducing load to an average 25% on my Asterisk server (Vicidial and Lighttpd are running on a separate server) I still have the following warning from time to time.
[Oct 30 18:31:56] WARNING[23179] app_meetme.c: Unable to write frame to channel SIP/Telco-09c9bc10
At first I though this was due to load, but now that load is very low on my server I do think this error is due to something else, but what.
One of my guess is priority inversion with an other process since all vicidial perl scripts are running on the server.
For that reason I moved mp3 compression to once a day when there is no production on the server.
But I let mixing of -in and -out.wav file to happen every 3 minutes. However, I do not see any correlation between this event and the warning which seems to occur randomly on the server.
I assume there might be an other process that leads to this error.
Any help to make Asterisk the top level priority process on the server is welcomed.
Bests
[Oct 30 18:31:56] WARNING[23179] app_meetme.c: Unable to write frame to channel SIP/Telco-09c9bc10
At first I though this was due to load, but now that load is very low on my server I do think this error is due to something else, but what.
One of my guess is priority inversion with an other process since all vicidial perl scripts are running on the server.
For that reason I moved mp3 compression to once a day when there is no production on the server.
But I let mixing of -in and -out.wav file to happen every 3 minutes. However, I do not see any correlation between this event and the warning which seems to occur randomly on the server.
I assume there might be an other process that leads to this error.
Any help to make Asterisk the top level priority process on the server is welcomed.
Bests