S25 Wi-Fi faults isolated to ONE network (home) – perfect on all others: doze data-path stalls + connectivity-check false-negatives

TL;DR: S25 flawless on every network except home WiFi. Home-only: (1) connectivity-check false-negatives ("no internet" while traffic works); (2) real data-path stall after idle/doze ("connected" but nothing passes until cellular failover). Valid IP held in both. Home went to WiFi 7 when it started. Run AdGuard DoT (permanent). What home-network factor triggers this on an S25 but nowhere else?

Trying to work out what's specific to one network. The anchor: these faults occur only on my home WiFi. Every other network: work, hotspots, elsewhere is perfect. So it's an interaction between the S25 and my home network, not general handset misbehaviour.

Supporting detail: home problems began when I moved home to WiFi 7 (two different WiFi 7 APs since – Arcadyan, eero 7). Other home devices mostly fine.

Two symptoms at home, association + DHCP retained throughout:

1. Connectivity-check false-negative: NetworkMonitor reports no internet (triggers mobile-data fallback) while real traffic works – pages load while the OS says offline.
2. Real data-path stall after idle/doze: connected, valid IPv4 lease, full RSSI, zero throughput until cellular failover or WiFi bounce. Also kills overnight streaming.

Environment / already tried:

• Private DNS: AdGuard DoT (dns.adguard.com) – permanent requirement. Tested off once (on a prior AP), Issue 1 persisted, so DoT isn't the sole cause.
• Fixed MAC (Phone MAC), DHCP reservation, MAC randomisation both ways.

Questions:

1. What home-network-specific factor (WiFi 7 MLO / 6GHz / WPA3 mode / band-steering / IPv6 / how it interacts with DoT) would trigger this on an S25 but not on any other network?
2. One root cause or two?
3. Client-side mitigations compatible with keeping Private DNS on – power-save flags, captive_portal_mode, 6GHz/MLO avoidance?