Server fails after installing certbot; MPM run failed, exiting

I set up a new server running Ubuntu 18.04 with 4GB of RAM with Apache2,PHP,MariaDB with Fail2ban and OSSEC. When I installed certbot to add an SSL cert from Let's Encrypt, Apache2 crashes.

Even when I restart the server, Apache will still crash.

Apache error log:
[Wed Jun 27 06:45:25.613316 2018] [mpmprefork:notice] [pid 3547] AH00163: Apache/2.4.29 (Ubuntu) OpenSSL/1.1.0g configured -- resuming normal operations [Wed Jun 27 06:45:25.613342 2018] [core:notice] [pid 3547] AH00094: Command line: '/usr/sbin/apache2' [Wed Jun 27 06:45:31.656454 2018] [mpmprefork:emerg] pid 7203Identifier removed: AH00144: couldn't grab the accept mutex
[Wed Jun 27 06:45:31.656663 2018] [mpmprefork:emerg] pid 7202Identifier removed: AH00144: couldn't grab the accept mutex [Wed Jun 27 06:45:31.659122 2018] [mpmprefork:emerg] pid 7201Identifier removed: AH00144: couldn't grab the accept mutex
[Wed Jun 27 06:45:32.623283 2018] [core:alert] [pid 3547] AH00050: Child 7201 returned a Fatal error… Apache is exiting!
[Wed Jun 27 06:45:32.623371 2018] [:emerg] [pid 3547] AH02818: MPM run failed, exiting
[Wed Jun 27 08:06:41.048660 2018] [mpmprefork:notice] [pid 1436] AH00163: Apache/2.4.29 (Ubuntu) OpenSSL/1.1.0g configured -- resuming normal operations [Wed Jun 27 08:06:41.050591 2018] [core:notice] [pid 1436] AH00094: Command line: '/usr/sbin/apache2' [Wed Jun 27 08:16:57.484364 2018] [mpmprefork:emerg] pid 1586Identifier removed: AH00144: couldn't grab the accept mutex
[Wed Jun 27 08:16:57.484407 2018] [mpmprefork:emerg] pid 1449Identifier removed: AH00144: couldn't grab the accept mutex [Wed Jun 27 08:16:57.487201 2018] [mpmprefork:emerg] pid 1625Identifier removed: AH00144: couldn't grab the accept mutex
[Wed Jun 27 08:16:57.487605 2018] [mpmprefork:emerg] pid 1447Identifier removed: AH00144: couldn't grab the accept mutex [Wed Jun 27 08:16:57.489578 2018] [mpmprefork:emerg] pid 1446Identifier removed: AH00144: couldn't grab the accept mutex
[Wed Jun 27 08:16:57.489626 2018] [mpmprefork:emerg] pid 1631Identifier removed: AH00144: couldn't grab the accept mutex [Wed Jun 27 08:16:57.492276 2018] [mpmprefork:emerg] pid 1630Identifier removed: AH00144: couldn't grab the accept mutex
[Wed Jun 27 08:16:57.636986 2018] [core:alert] [pid 1436] AH00050: Child 1446 returned a Fatal error… Apache is exiting!
[Wed Jun 27 08:16:57.637053 2018] [:emerg] [pid 1436] AH02818: MPM run failed, exiting

What OSSEC says:
[:emerg] [pid 1436] AH02818: MPM run failed, exiting
[core:alert] [pid 1436] AH00050: Child 1446 returned a Fatal error… Apache is exiting!
system systemd[1]: apache2.service: Failed with result 'exit-code'.
system systemd[1]: apache2.service: Main process exited, code=exited, status=1/FAILURE

Syslog error report:
Jun 27 08:16:45 system systemd[1]: Created slice User Slice of [username redacted].
Jun 27 08:16:45 system systemd[1]: Starting User Manager for UID 1000…
Jun 27 08:16:45 system systemd[1]: Started Session c2 of user [username redacted].
Jun 27 08:16:45 system systemd[1646]: Listening on GnuPG cryptographic agent and passphrase cache (access for web browsers).
Jun 27 08:16:45 system systemd[1646]: Listening on GnuPG network certificate management daemon.
Jun 27 08:16:45 system systemd[1646]: Listening on GnuPG cryptographic agent (ssh-agent emulation).
Jun 27 08:16:45 system systemd[1646]: Reached target Timers.
Jun 27 08:16:45 system systemd[1646]: Listening on GnuPG cryptographic agent and passphrase cache (restricted).
Jun 27 08:16:45 system systemd[1646]: Reached target Paths.
Jun 27 08:16:45 system systemd[1646]: Listening on GnuPG cryptographic agent and passphrase cache.
Jun 27 08:16:45 system systemd[1646]: Reached target Sockets.
Jun 27 08:16:45 system systemd[1646]: Reached target Basic System.
Jun 27 08:16:45 system systemd[1646]: Reached target Default.
Jun 27 08:16:45 system systemd[1646]: Startup finished in 78ms.
Jun 27 08:16:45 system systemd[1]: Started User Manager for UID 1000.
Jun 27 08:16:57 system systemd[1]: Stopping User Manager for UID 1000…
Jun 27 08:16:57 system systemd[1646]: Stopped target Default.
Jun 27 08:16:57 system systemd[1646]: Stopped target Basic System.
Jun 27 08:16:57 system systemd[1646]: Stopped target Sockets.
Jun 27 08:16:57 system systemd[1646]: Closed GnuPG cryptographic agent (ssh-agent emulation).
Jun 27 08:16:57 system systemd[1646]: Closed GnuPG cryptographic agent and passphrase cache (restricted).
Jun 27 08:16:57 system systemd[1646]: Closed GnuPG network certificate management daemon.
Jun 27 08:16:57 system systemd[1646]: Stopped target Paths.
Jun 27 08:16:57 system systemd[1646]: Closed GnuPG cryptographic agent and passphrase cache.
Jun 27 08:16:57 system systemd[1646]: Stopped target Timers.
Jun 27 08:16:57 system systemd[1646]: Closed GnuPG cryptographic agent and passphrase cache (access for web browsers).
Jun 27 08:16:57 system systemd[1646]: Reached target Shutdown.
Jun 27 08:16:57 system systemd[1646]: Starting Exit the Session…
Jun 27 08:16:57 system systemd[1646]: Received SIGRTMIN+24 from PID 1764 (kill).
Jun 27 08:16:57 system systemd[1]: Stopped User Manager for UID 1000.
Jun 27 08:16:57 system systemd[1]: Removed slice User Slice of [username redacted].
Jun 27 08:16:57 system systemd[1]: apache2.service: Main process exited, code=exited, status=1/FAILURE
Jun 27 08:16:57 system systemd[1]: apache2.service: Failed with result 'exit-code'.