в чем может быть проблема? В консоли астериска появляются иногда записи типа:

[Dec 22 09:40:51] WARNING[96122]: chan_zap.c:8171 pri_fixup_principle: Call specified, but not found?
[Dec 22 09:40:51] WARNING[96122]: chan_zap.c:9292 pri_dchannel: Hangup on bad channel 1/15 on span 1
[Dec 22 09:40:55] WARNING[96122]: chan_zap.c:8171 pri_fixup_principle: Call specified, but not found?
[Dec 22 09:40:55] WARNING[96122]: chan_zap.c:9292 pri_dchannel: Hangup on bad channel 1/15 on span 1

Не сталкивался.
Быстрый гугл дает варианты:

ssue was that zapata.conf was specifying "trunkgroup" for the spans.
This was adding a "DS1 Identifier" to the setup channel ID, which
the CO does not recognize and so it assigns its own pick of channel.
This was causing a move which asterisk does not cope with.
(Actually, initial channel id being "exclusive" explicitly forbids
B channel being moved).

Попробуйте, расскажите...