Your debug log shows something's amiss with your Pi-hole's network connectivity:
*** [ DIAGNOSING ]: Networking
[✓] IPv4 address(es) bound to the eth0 interface:
192.168.86.200/24 matches the IP found in /etc/pihole/setupVars.conf
[i] Default IPv4 gateway: 192.168.86.1
192.168.86.1
* Pinging 192.168.86.1
192.168.86.1...
[✗] Gateway did not respond
*** [ DIAGNOSING ]: Name resolution (IPv4) using a random blocked domain and a known ad-serving domain
[✗] Failed to resolve cpatext.ru via localhost (127.0.0.1)
[✗] Failed to resolve cpatext.ru via Pi-hole (192.168.86.200)
[✓] doubleclick.com is 172.217.14.206 via a remote, public DNS server (8.8.8.8)
It also shows you are running a few additional software packages on the same machine:
*** [ DIAGNOSING ]: Ports in use
*:32400 Plex Me (IPv6)
127.0.0.1:32401 Plex Me (IPv4)
*:22 sshd (IPv4)
*:22 sshd (IPv6)
*:548 afpd (IPv6)
[::1]:4700 cnid_metad (IPv6)
[80] is in use by lighttpd
[80] is in use by lighttpd
127.0.0.1:35983 Plex Sc (IPv4)
127.0.0.1:32600 Plex Tu (IPv4)
*:445 smbd (IPv6)
*:139 smbd (IPv6)
*:445 smbd (IPv4)
*:139 smbd (IPv4)
[53] is in use by pihole-FTL
[53] is in use by pihole-FTL
[4711] is in use by pihole-FTL
[4711] is in use by pihole-FTL
(I am reasonably sure the public DNS servers in your test don't also run a Plex media server) 
This may very well contribute to memory shortages, resulting in forced stops of Pi-hole's lighttpd, in the vain hope to acquire enough memory on restart:
*** [ DIAGNOSING ]: contents of /var/log/lighttpd
-rw-r--r-- 1 www-data www-data 2073 Oct 1 09:53 /var/log/lighttpd/error.log
2020-09-27 00:00:22: (server.c.1759) logfiles cycled UID = 0 PID = 15264
2020-09-27 13:23:51: (mod_fastcgi.c.421) FastCGI-stderr: PHP Fatal error: Allowed memory size of 134217728 bytes exhausted (tried to allocate 4096 bytes) in /var/www/html/admin/scripts/pi-hole/php/FTL.php on line 80
2020-09-27 16:39:41: (server.c.2059) server stopped by UID = 0 PID = 1
2020-09-27 16:39:42: (server.c.1464) server started (lighttpd/1.4.53)
You may try to increase PHP memory allocation, but you should keep a keen eye on your other processes memory consumption as well.