Recording Calls - weird problem - FreePBX 2.7.0.1

Change your globals_custom.conf to point to a simple shell script:
MONITOR_EXEC=/var/lib/asterisk/bin/soxmix.sh

Where soxmix.sh is:

#!/bin/sh
nice -n 19 soxmix $1 $2 $3
if [ -s $3 ]
then
 rm -f $1
 rm -f $2
fi