When can a BEEP peer send <close number='0'>

RFC 3080 section 2.3.1.3 clearly specifies when a BEEP peer may send a 
"close" message for a channel, but the RFC isn't quite clear about when 
a BEEP peer may send <close number='0'>.  I''m asking this because I run 
into a problem with beepcore-c: peer A sends <close number='0'> after it 
receives <close number='1'> but before it acknowledges the channel close 
request; and peer B releases all channel on seeing <close number='0'>, 
then it sees the <ok> for the <close number='1'> request it sent out and 
core dumps while trying to reference channel 1.  This does not look like 
100% implementation issue - the RFC can be more affirmative on this?

Thanks..