Rocky Linux 8 - /dev/ttyS0 is not a tty

[byrnejb]

Following a UART disconnect I am seeing messages referring to /dev/ttyS0 not being a tty:

Feb 21 11:01:01 vhp3k103.harte-lyne.ca CROND[2061060]: (root) CMD (run-parts /etc/cron
.hourly)
Feb 21 11:01:01 vhp3k103.harte-lyne.ca run-parts[2061063]: (/etc/cron.hourly) starting
 0anacron
Feb 21 11:01:01 vhp3k103.harte-lyne.ca run-parts[2061069]: (/etc/cron.hourly) finished
 0anacron
Feb 21 11:57:16 vhp3k103.harte-lyne.ca charon-par[2059814]: uart0: Client disconnected
Feb 21 11:57:19 vhp3k103.harte-lyne.ca login[6831]: pam_unix(login:session): session c
losed for user root
Feb 21 11:57:19 vhp3k103.harte-lyne.ca systemd[1]: serial-getty@ttyS0.service: Succeed
ed.
Feb 21 11:57:19 vhp3k103.harte-lyne.ca systemd-logind[800]: Session 80 logged out. Wai
ting for processes to exit.
Feb 21 11:57:19 vhp3k103.harte-lyne.ca systemd[1]: serial-getty@ttyS0.service: Service
 RestartSec=100ms expired, scheduling restart.
Feb 21 11:57:19 vhp3k103.harte-lyne.ca systemd[1]: serial-getty@ttyS0.service: Schedul
ed restart job, restart counter is at 1.
Feb 21 11:57:19 vhp3k103.harte-lyne.ca systemd[1]: Stopped Serial Getty on ttyS0.
Feb 21 11:57:19 vhp3k103.harte-lyne.ca systemd[1]: Started Serial Getty on ttyS0.
Feb 21 11:57:19 vhp3k103.harte-lyne.ca agetty[2061470]: /dev/ttyS0: not a tty
Feb 21 11:57:29 vhp3k103.harte-lyne.ca systemd[1]: serial-getty@ttyS0.service: Succeed
ed.
Feb 21 11:57:29 vhp3k103.harte-lyne.ca systemd[1]: serial-getty@ttyS0.service: Service
 RestartSec=100ms expired, scheduling restart.
Feb 21 11:57:29 vhp3k103.harte-lyne.ca systemd[1]: serial-getty@ttyS0.service: Schedul
ed restart job, restart counter is at 2.

However,

ll /dev/ttyS0
crw--w----. 1 root tty 4, 64 Feb 25 12:20 /dev/ttyS0

These messages are filling log files and I would like to know the following things:

1. What is the actual problem with /dev/ttyS0?

2. How do I fix it?

3. What caused it?

Any help with any of these is welcomed.

Thanks.