(gdb) bt
#0  0x0000000000000000 in ?? ()
#1  0x0000000000472b22 in ast_senddigit_begin (chan=0x7faaa00462b8, digit=35 '#') at channel.c:4750
#2  0x0000000000487650 in ast_senddigit (chan=0x7faaa00462b8, digit=35 '#', duration=89) at channel.c:4791
#3  0x000000000043008c in ast_dtmf_stream (chan=0x7faaa00462b8, peer=0x7faac00d3418, digits=<value optimized out>, between=100, duration=89) at app.c:773
#4  0x00000000004c39e7 in ast_bridge_call (chan=0x7faac00d3418, peer=0x7faaa00462b8, config=0x7faac6c03b90) at features.c:4678
#5  0x00000000004c54fc in bridge_exec (chan=0x7faac00d3418, data=<value optimized out>) at features.c:8301
#6  0x000000000051aef4 in pbx_exec (c=0x7faac00d3418, app=0xce9640, data=0x7faabc04c86c "SIP/sansay-sd-00002e78,kK") at pbx.c:1589
#7  0x00007faafcc64ce2 in handle_exec (chan=0x7faac00d3418, agi=0x7faac6c054c0, argc=3, argv=0x7faac6c03e60) at res_agi.c:2521
#8  0x00007faafcc677a1 in agi_handle_command (chan=0x7faac00d3418, agi=0x7faac6c054c0, buf=0x7faabc04c860 "EXEC", dead=0) at res_agi.c:3418
#9  0x00007faafcc6935c in launch_asyncagi (chan=0x7faac00d3418, data=<value optimized out>, enhanced=<value optimized out>, dead=0) at res_agi.c:1329
#10 launch_script (chan=0x7faac00d3418, data=<value optimized out>, enhanced=<value optimized out>, dead=0) at res_agi.c:1631
#11 agi_exec_full (chan=0x7faac00d3418, data=<value optimized out>, enhanced=<value optimized out>, dead=0) at res_agi.c:3899
#12 0x000000000051aef4 in pbx_exec (c=0x7faac00d3418, app=0xccb6f0, data=0x7faac6c07680 "agi:async") at pbx.c:1589
#13 0x0000000000525664 in pbx_extension_helper (c=0x7faac00d3418, con=0x0, context=<value optimized out>, exten=<value optimized out>, priority=3, label=0x0, 
    callerid=0x7faac01bb320 "7805", action=E_SPAWN, found=0x7faac6c09cfc, combined_find_spawn=1) at pbx.c:4665
#14 0x000000000052c525 in ast_spawn_extension (c=0x7faac00d3418, args=0x0) at pbx.c:5781
#15 __ast_pbx_run (c=0x7faac00d3418, args=0x0) at pbx.c:6256
#16 0x000000000052dcab in pbx_thread (data=<value optimized out>) at pbx.c:6586
#17 0x000000000056d90b in dummy_start (data=<value optimized out>) at utils.c:1028
#18 0x00007faafe68d851 in start_thread (arg=0x7faac6c0a700) at pthread_create.c:301
#19 0x00007faaffbff11d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:115
(gdb) fr 1
#1  0x0000000000472b22 in ast_senddigit_begin (chan=0x7faaa00462b8, digit=35 '#') at channel.c:4750
4750		if (!ast_channel_tech(chan)->send_digit_begin(chan, digit))
(gdb) p chan->name
$1 = (const ast_string_field) 0x7faaa003a63a "AsyncGoto/SIP/sansay-sd-00002e78<ZOMBIE>"
(gdb) p *chan->tech
$2 = {type = 0x59802d "NULL", description = 0x59bc38 "Null channel (should not see this)", capabilities = 0x0, properties = 0, requester = 0, devicestate = 0, 
  send_digit_begin = 0, send_digit_end = 0, call = 0, hangup = 0, answer = 0, read = 0, write = 0, send_text = 0, send_image = 0, send_html = 0, exception = 0, 
  bridge = 0, early_bridge = 0, indicate = 0, fixup = 0, setoption = 0, queryoption = 0, transfer = 0, write_video = 0, write_text = 0, bridged_channel = 0, 
  func_channel_read = 0, func_channel_write = 0, get_base_channel = 0, set_base_channel = 0, get_pvt_uniqueid = 0, cc_callback = 0, pre_call = 0}