My setup consists of two Pi-hole instances each runnnig within container on two separte Synolog NAS-s, both running DSM 7.2.1. One Pi-hole (lets called it "main", is first to appear in DHCP server DNS list) the other "secondary". They are similarly configured, although "main" is fully updated to the latest Pi-hole version (Docker Tag: 2025.06.1, Core: v6.1.2 FTL: v6.2.2, Web interface: v6.2.1) , the other is slightly behind. Docker container is version 20.10.23-1437 on both NAS-s. Both Pi-hole instances forward to Synology DNS server, running on the "secondary" NAS.
Obviously, the "main" Pi-hole is hit the hardest (it shows >33000 queries, of which ~10% are blocked).
For the last couple of weeks, my "main" Pi-hole is behaving strangly: loggin in, it takes a very long time (over a minute? maybe more) for the admin panel to show. Query log display takes forever, at which time it does not respond to DNS queries (once display appears, it does)
None of the NAS servers are particularly loaded: their CPU load is less than 10%, and so is RAM usage.
Not sure what is going on...
Debug token: https://tricorder.pi-hole.net/yEiBGEqU/