Pi-hole server lockups about once a month

Hello. We have a pihole server that seems to lockup about once a month. The fix appears to be to restart the DNS resolver and then everything starts working fine again. Sometimes this can be done through the UI but other times that won’t respond and it must be done through the command line. When we are able to get into the UI’s Settings screen, we see the error following at the top of the screen

PHP error (2): fsockopen(): unable to connect to (Connection refused) in /var/www/html/admin/scripts/pi-hole/php/FTL.php:47

This a physical server also running Apache on port 80 but no other services.

Any suggestions would be great.

Debug Token:

Debug token is: https://tricorder.pi-hole.net/5W3TVlvB/

I have that error as well on rare occasions.
I have noticed the ftl process runs at 100 %.
I fix it by renaming the ftl.db file and restarting the ftl service.

When this happens what does the Dashboard Status show in the upper corner when you reload the page? Does it show Active and green or does it show DNS service not running and red? What about the stats boxes across the top, do they show numbers or do they say Lost connection to API?