Unable to access self hosted websites across vlans

[viragomann]

Yes, I suspect, that the VLANs are leaking somewhere outside of OPNsense, so that not every packet passes it.

As mentioned, check out the TCP flag of the blocked packets. Presumably they are not SYN packets. This would mean, that the respective SYN packet of the connection didn't pass OPNsense.
Normally only SYN packets are logged. If they are allowed, OPNsense sets a state, which passes following belonging packets.