DHCP Cluster crashes randomly

We're running in to a case that's very similar to https://bugs.launchpad.net/dhcp/+bug/1872118 where the DHCP server periodically crashes. Crashes sometimes take days to happen on relatively busy DHCP servers. There's not an obvious reason, however the logs end up showing (hostnames and email address changed slightly to keep meaning, but not disclose everything).

May 14 05:22:17 is-landlord-04.wm.edu sh[305109]: ../../../../lib/isc/unix/socket.c:4359: fatal error: select() failed: Bad file descriptor
May 14 05:22:27 hostname.wm.edu systemd[1]: isc-dhcp-server.service: Main process exited, code=killed, status=6/ABRT
May 14 05:22:32 is-landlord-04.wm.edu sSMTP[1645996]: Sent mail for <email address hidden> (221 2.0.0 Service closing transmission channel) uid=0 username=root ou>
May 14 05:22:32 is-landlord-04.wm.edu systemd[1]: isc-dhcp-server.service: Failed with result 'signal'.
May 14 05:22:37 is-landlord-04.wm.edu systemd[1]: isc-dhcp-server.service: Scheduled restart job, restart counter is at 25.
May 14 05:22:37 is-landlord-04.wm.edu systemd[1]: Stopped ISC DHCP IPv4 server.
May 14 05:22:37 is-landlord-04.wm.edu systemd[1]: Started ISC DHCP IPv4 server.

$ sudo cat _usr_sbin_dhcpd.0.crash
ProblemType: Crash
Architecture: amd64
Date: Fri May 14 05:22:21 2021
DistroRelease: Ubuntu 20.04
ExecutablePath: /usr/sbin/dhcpd
ExecutableTimestamp: 1615303185
ProcCmdline: dhcpd -user dhcpd -group dhcpd -f -4 -pf /run/dhcp-server/dhcpd.pid -cf /etc/dhcp/dhcpd.conf
ProcEnviron: Error: [Errno 13] Permission denied: 'environ'
ProcMaps: Error: [Errno 13] Permission denied: 'maps'
ProcStatus:
 Name: dhcpd
 Umask: 0022
 State: D (disk sleep)
 Tgid: 305109
 Ngid: 0
 Pid: 305109
 PPid: 1
 TracerPid: 0
 Uid: 116 116 116 116
 Gid: 119 119 119 119
 FDSize: 256
 Groups:
 NStgid: 305109
 NSpid: 305109
 NSpgid: 305109
 NSsid: 305109
 VmPeak: 422372 kB
 VmSize: 356836 kB
 VmLck: 0 kB
 VmPin: 0 kB
 VmHWM: 289404 kB
 VmRSS: 258028 kB
 RssAnon: 255560 kB
 RssFile: 2468 kB
 RssShmem: 0 kB
 VmData: 282632 kB
 VmStk: 132 kB
 VmExe: 592 kB
 VmLib: 5352 kB
 VmPTE: 584 kB
 VmSwap: 2496 kB
 HugetlbPages: 0 kB
 CoreDumping: 1
 THP_enabled: 1
 Threads: 4
 SigQ: 0/3521
 SigPnd: 0000000000000000
 ShdPnd: 0000000000000000
 SigBlk: 0000000000000000
 SigIgn: 0000000000001000
 SigCgt: 0000000180000000
 CapInh: 0000000000000000
 CapPrm: 0000000000000000
 CapEff: 0000000000000000
 CapBnd: 0000003fffffffff
 CapAmb: 0000000000000000
 NoNewPrivs: 0
 Seccomp: 0
 Speculation_Store_Bypass: thread vulnerable
 Cpus_allowed: ffffffff,ffffffff
 Cpus_allowed_list: 0-63
 Mems_allowed: 00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000001
 Mems_allowed_list: 0
 voluntary_ctxt_switches: 94
 nonvoluntary_ctxt_switches: 831
Signal: 6
Uname: Linux 5.4.0-71-generic x86_64
UserGroups: N/A

Because of the similarities with #1872118 we started by checking various package versions:

$ sudo dpkg -l | grep -i isc-
ii isc-dhcp-client 4.4.1-2.1ubuntu5.20.04.1 amd64 DHCP client for automatically obtaining an IP address
ii isc-dhcp-common 4.4.1-2.1ubuntu5.20.04.1 amd64 common manpages relevant to all of the isc-dhcp packages
ii isc-dhcp-server 4.4.1-2.1ubuntu5.20.04.1 amd64 ISC DHCP server for automatic IP address assignment
ii libisc-export1105:amd64 1:9.11.16+dfsg-3~ubuntu1 amd64 Exported ISC Shared Library

$ sudo dpkg -l | grep -i bind9-libs
ii bind9-libs:amd64 1:9.16.1-0ubuntu2.8 amd64 Shared Libraries used by BIND 9

$ sudo dpkg -l | grep -i libisc-*
ii libisc-export1105:amd64 1:9.11.16+dfsg-3~ubuntu1 amd64 Exported ISC Shared Library
ii libisccfg-export163 1:9.11.16+dfsg-3~ubuntu1 amd64 Exported ISC CFG Shared Library

$ sudo dpkg -l | grep -i libirs-*
ii libirs-export161 1:9.11.16+dfsg-3~ubuntu1 amd64 Exported IRS Shared Library

$ sudo dpkg -l | grep -i libdns-*
ii libdns-export1109 1:9.11.16+dfsg-3~ubuntu1 amd64 Exported DNS Shared Library

Finally, we're running Ubuntu 20.04.2:
$ lsb_release -rd
Description: Ubuntu 20.04.2 LTS
Release: 20.04

Let us know what else can be provided to help confirm or troubleshoot the issue.