@harison Just off the top of my head I'd say to make sure that this setting is unchecked in Services/DNS Resolver/General Settings:
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The above causes unbound to stop and reload itself every time a client requests a DHCP lease. During that time DNS resolution does not happen and therefore nothing trying to be reached by a domain name (www.google.com) can be reached on the net (unless it is already cached in the DNS).
Other than that, I think we're going to need a lot more info to help you. As a start, I'd suggest screenshots of your DNS and pfblocker settings as well as Status/System Logs/System/DNS Resolver and Status/System Logs/Gateways when the issue is happening.
When the web "crashes" can you ping 8.8.8.8 from the WAN as the source address in Diagnostics/Ping? What about www.google.com?