Comment 2 for bug 1954854

This started happening when I upgraded the server from Ubuntu 18.04 to 20.04. Is there a convenient way to downgrade to 9.10.3?

As far as triggering the crash, I'm not sure. As I said it seems to happen randomly. I suspect it's related to the amount of load on the service.
Here's a grep from my syslog which shows when the crashes happen:

/var/log/syslog.1:Dec 15 07:29:37 dc-dns-02 named[15512]: REFUSED unexpected RCODE resolving 'q-seeqcview.com/A/IN': 205.251.193.49#53
/var/log/syslog.1:Dec 15 07:29:37 dc-dns-02 kernel: [573662.780659] isc-worker0000[15523]: segfault at 8 ip 00007f84a45bf166 sp 00007f84a12cd530 error 4 in libisc.so.1601.0.0[7f84a459d000+46000]
/var/log/syslog.1:Dec 15 07:29:37 dc-dns-02 kernel: [573662.780675] Code: 00 00 48 8d 3d ab b4 02 00 e8 66 39 fe ff 66 0f 1f 44 00 00 f3 0f 1e fa 41 57 41 56 41 55 41 54 55 53 48 83 ec 08 4c 8b 67 10 <41> 83 7c 24 08 02 0f 85 be 00 00 00 49 89 fd 49 8b 7c 24 10 48 89

/var/log/syslog.2.gz:Dec 14 16:19:09 dc-dns-02 named[12817]: network unreachable resolving 'q-seeqcview.com/A/IN': 2600:9000:5302:fc00::1#53
/var/log/syslog.2.gz:Dec 14 16:19:10 dc-dns-02 kernel: [519037.010692] isc-worker0000[12829]: segfault at 8 ip 00007f2e512d6166 sp 00007f2e4dfe4530 error 4 in libisc.so.1601.0.0[7f2e512b4000+46000]
/var/log/syslog.2.gz:Dec 14 16:19:10 dc-dns-02 kernel: [519037.010706] Code: 00 00 48 8d 3d ab b4 02 00 e8 66 39 fe ff 66 0f 1f 44 00 00 f3 0f 1e fa 41 57 41 56 41 55 41 54 55 53 48 83 ec 08 4c 8b 67 10 <41> 83 7c 24 08 02 0f 85 be 00 00 00 49 89 fd 49 8b 7c 24 10 48 89

/var/log/syslog.3.gz:Dec 13 14:26:10 dc-dns-02 kernel: [425857.862410] show_signal_msg: 20 callbacks suppressed
/var/log/syslog.3.gz:Dec 13 14:26:10 dc-dns-02 kernel: [425857.862416] isc-worker0000[2530]: segfault at 8 ip 00007f305aef1166 sp 00007f3057bff530 error 4 in libisc.so.1601.0.0[7f305aecf000+46000]
/var/log/syslog.3.gz:Dec 13 14:26:10 dc-dns-02 kernel: [425857.862429] Code: 00 00 48 8d 3d ab b4 02 00 e8 66 39 fe ff 66 0f 1f 44 00 00 f3 0f 1e fa 41 57 41 56 41 55 41 54 55 53 48 83 ec 08 4c 8b 67 10 <41> 83 7c 24 08 02 0f 85 be 00 00 00 49 89 fd 49 8b 7c 24 10 48 89

The crash (at least for these three instances) is happening at the same address.
00007f84a45bf166 - 7f84a459d000 = 22166
and
00007f305aef1166 - 7f305aecf000 = 22166