Phones periodically can not call out, no ringtone, total mystery

What does this mean? Every so often my phones can’t call out and I see this in the logs:

[Nov 16 11:46:14] VERBOSE[4832] pbx.c: – Executing [[email protected]:12] Hangup(“SIP/110-00000290”, “”) in new stack
[Nov 16 11:46:14] VERBOSE[4832] app_macro.c: == Spawn extension (macro-hangupcall, s, 12) exited non-zero on ‘SIP/110-00000290’ in macro ‘hangupcall’
[Nov 16 11:46:14] VERBOSE[4832] app_macro.c: == Spawn extension (macro-dialout-trunk, s, 20) exited non-zero on ‘SIP/110-00000290’ in macro ‘dialout-trunk’
[Nov 16 11:46:14] VERBOSE[4832] pbx.c: == Spawn extension (from-internal, 13092871420, 4) exited non-zero on ‘SIP/110-00000290’