From your debug log, you have configured Pi-hole to do so:
-rw-r--r-- 1 pihole pihole 20 Feb 6 19:43 /etc/pihole/pihole-FTL.conf
REPLY_ADDR4=0.0.0.0
Were you experiencing cache evictions that led you to increase the cache size?
*** [ DIAGNOSING ]: Setup variables
CACHE_SIZE=50000