Outgoing to ISDN calls fail with cause 0x2C

Question

Cisco 2821 with 4 E1 connected to PSTN. Most outgoing calls flow without any issues, but sometimes fails (debug isdn error shows "CCPMSG_OutCall: fails with cause 0x2C"). I see enough free timeslots in E1 at this time. This E1 using for outgoing calls only, incoming calls come via other E1.
Router configuration:
controller E1 0/1/1
framing NO-CRC4
pri-group timeslots 1-31
interface Serial0/1/1:15
no ip address
encapsulation hdlc
no logging event link-status
isdn switch-type primary-net5
isdn timer T303 120000
isdn incoming-voice voice
isdn map address .* plan isdn type national
isdn send-alerting
isdn negotiate-bchan resend-setup
isdn bchan-number-order ascending round-robin
isdn sending-complete
no isdn outgoing display-ie
trunk-group PSTN 10
no cdp enable

Answer 1

"debug isdn q931 detailed" & "debug isdn error" show:
ISDN Se0/1/1:15 Q931d: Default type/plan 0x0 0x1 sw-type 18 Calling number 4242510458 isdn_map 0 mask 0x3022
ISDN Se0/1/1:15 Q931d: Calling plan/type unspecified in call_decode, so ignored.
ISDN Se0/1/1:15 Q931d: No call_decode, isdn default set
ISDN Se0/1/1:15 Q931d: isdn_parser_map_lkup: Comparing 4242510458/.*, (regexp)
ISDN Se0/1/1:15 Q931d: isdn_parser_map_lkup: overriding plan/type for 4242510458, isdn/unknown to isdn/national; Oct3a 0x81
ISDN Se0/1/1:15 Q931d: Default type/plan 0x0 0x1 sw-type 18 Called number 9262151 isdn_map 0 mask 0x3022
ISDN Se0/1/1:15 Q931d: Called plan/type unspecified in call_decode, so ignored.
ISDN Se0/1/1:15 Q931d: No call_decode, isdn default set
ISDN Se0/1/1:15 Q931d: isdn_parser_map_lkup: Comparing 9262151/.*, (regexp)
ISDN Se0/1/1:15 Q931d: isdn_parser_map_lkup: overriding plan/type for 9262151, isdn/unknown to isdn/national
ISDN Se0/1/1:15 Q931d: isdn_parser_map_lkup: Comparing 4242510458/.*, (regexp)
ISDN Se0/1/1:15 Q931d: isdn_parser_map_lkup: overriding plan/type for 4242510458, isdn/unknown to isdn/national
ISDN Se0/1/1:15 **ERROR**: CCPMSG_OutCall: fails with cause 0x2C
ISDN Se0/1/1:15 Q931d: L3IF_rx_L2_pak: received data
080285335A
ISDN Se0/1/1:15 Q931d: L3_Go: source 0x020A, event 0x005A, call id 0x0000, int id 0x0
ISDN Se0/1/1:15 Q931d: L3_Go: event 0x5A cr_len 2 cr 1331
ISDN Se0/1/1:15 Q931d: L3_Go: call_id 0x84C9 cr 0x533 state 19 event 0x5A ces 1
ISDN Se0/1/1:15 Q931d: L3_ProcessEvent: callref = 0x0533 RELEASE_COMP:U19_ReleaseComp(nlcb)
ISDN Se0/1/1:15 Q931d: L3_state_change: callref 0x0533 old RELEASE_REQUEST, new NULL_STATE