Comment 15 for bug 1164023

Ah, you're right, my bad :)

Relevant logs then:

Apr 3 21:26:18 till-twist modem-manager[5778]: <debug> [mm-at-serial-port.c:334] debug_log(): (ttyACM1): --> 'AT+CIND?<CR>'
Apr 3 21:26:21 till-twist modem-manager[5778]: <debug> [mm-at-serial-port.c:334] debug_log(): (ttyACM1): --> 'AT+CSQ<CR>'
Apr 3 21:26:21 till-twist modem-manager[5778]: <debug> [mm-at-serial-port.c:334] debug_log(): (ttyACM1): <-- '<CR><LF>+CSQ: 11,99<CR><LF>'
Apr 3 21:26:21 till-twist modem-manager[5778]: <debug> [mm-at-serial-port.c:334] debug_log(): (ttyACM1): <-- '<CR><LF>OK<CR><LF>'
Apr 3 21:26:21 till-twist modem-manager[5778]: mm_callback_info_schedule: assertion `info->called == FALSE' failed
Apr 3 21:26:48 till-twist modem-manager[5778]: <debug> [mm-at-serial-port.c:334] debug_log(): (ttyACM1): --> 'AT+CIND?<CR>'
Apr 3 21:26:48 till-twist modem-manager[5778]: <debug> [mm-at-serial-port.c:334] debug_log(): (ttyACM1): <-- '<CR><LF>+CIND: 5,3,0,0,1,1,0,0,0,0,0,0<CR><LF>'
Apr 3 21:26:48 till-twist modem-manager[5778]: <debug> [mm-at-serial-port.c:334] debug_log(): (ttyACM1): <-- '<CR><LF>OK<CR><LF>'
Apr 3 21:26:57 till-twist usbmuxd[5806]: [2] Attempted to connect to nonexistent device 1
Apr 3 21:27:18 till-twist modem-manager[5778]: <debug> [mm-at-serial-port.c:334] debug_log(): (ttyACM1): --> 'AT+CIND?<CR>'
Apr 3 21:27:18 till-twist modem-manager[5778]: <debug> [mm-at-serial-port.c:334] debug_log(): (ttyACM1): <-- '<CR><LF>+CIND: 5,3,0,0,1,1,0,0,0,0,0,0<CR><LF>'
Apr 3 21:27:18 till-twist modem-manager[5778]: <debug> [mm-at-serial-port.c:334] debug_log(): (ttyACM1): <-- '<CR><LF>OK<CR><LF>'
Apr 3 21:27:48 till-twist kernel: [11019.226084] modem-manager[5778]: segfault at 100000001 ip 00007fd690d58f7f sp 00007fff38b165f0 error 4 in libglib-2.0.so.0.3600.0[7fd690cf5000+f9000]

The "assertion `info->called == FALSE' failed" message is interesting...