Oh, okay. This is not resolving the issue. dnsmgr status shows
DNS Manager: enabled
Refresh Interval: 300 seconds
Number of entries: 4
and both dnsmgr refresh and dnsmgr reload do not resolve the issue.
But this appears in the logs:
[2021-11-09 20:01:48] DEBUG[28106] dnsmgr.c: Refreshing DNS lookups.
20919[2021-11-09 20:01:48] DEBUG[28106] dnsmgr.c: refreshing '<External IP address of SIP server>'
20920[2021-11-09 20:01:48] DEBUG[28106] netsock2.c: Splitting '<External IP address of SIP server>' into...
20921[2021-11-09 20:01:48] DEBUG[28106] netsock2.c: ...host '<External IP address of SIP server>' and port ''.
20922[2021-11-09 20:01:48] DEBUG[28106] dnsmgr.c: refreshing '<External IP address of SIP server>'
20923[2021-11-09 20:01:48] DEBUG[28106] netsock2.c: Splitting '<External IP address of SIP server>' into...
20924[2021-11-09 20:01:48] DEBUG[28106] netsock2.c: ...host '<External IP address of SIP server>' and port ''.
20925[2021-11-09 20:01:48] DEBUG[28106] dnsmgr.c: refreshing '<External IP address of SIP server>'
20926[2021-11-09 20:01:48] DEBUG[28106] netsock2.c: Splitting '<External IP address of SIP server>' into...
20927[2021-11-09 20:01:48] DEBUG[28106] netsock2.c: ...host '<External IP address of SIP server>' and port ''.
20928[2021-11-09 20:01:48] DEBUG[28106] dnsmgr.c: refreshing '<External IP address of SIP server>'
20929[2021-11-09 20:01:48] DEBUG[28106] netsock2.c: Splitting '<External IP address of SIP server>' into...
20930[2021-11-09 20:01:48] DEBUG[28106] netsock2.c: ...host '<External IP address of SIP server>' and port ''.
Unfortunately it doesn’t tell how it resolves. But all of this seems to be very weird to me. Whatever I try, I cannot make it work without reloading the transports or Asterisk entirely.