WAX625 AP not allowing multicast discovery and control

I have recently setup two VLANs on my router - one for my trusted devices (like mobile phones, laptops etc.) and the other for IoT devices, like Google Nest speakers. I have setup a firewall rule to allow main VLAN traffic to reach IoT VLAN and also allowed return traffic. However, I am not able to discover or control my Google Nest speakers from main VLAN when connected through WiFi AP.

Key configurations and measures I have taken:

1. mDNS is enabled on my router (scoping both VLANs) but disabled on AP.
2. mDNS on router is configured to allow specific Googlecast service on the router.
3. IGMP Snooping is enabled on the router (scoping both VLANs) but disabled on AP.
4. Removed Multicast Rate Limiting on AP.
5. Fixed Multicast Rate = Auto on AP.
6. Client Isolation is disabled on AP but enabled on the router for the IoT VLAN only.
7. DHCP Offer Broadcast to Unicast = Disabled on AP.
8. The AP is running on latest firmware v12.8.0.6.

Key tests and outcomes I ran are as follows:

1. I used Spotify on my laptop to access Google Nest speaker while connecting through WiFi AP and I am not able to see or control them. When I connect the same laptop through the Ethernet, still using separate VLANs, everything works as expected.
2. Another strange scenario is that when using Spotify on my phone I can see the IoT speaker but cannot connect them.
3. I can ping my Google Nest speaker from my laptop and get a response back with both connections i.e. WiFi AP and Ethernet.
4. Note: For all the tests I have conducted above, my laptop/phone have been on main VLAN while the Google Nest speaker on a separate IoT VLAN.
5. The test I have conducted indicate that my router is allowing connectivity between VLANs but the WiFi AP is restricting it. Specifically, mDNS discovery and their control is not working.

I have changed almost every setting that I thought could be impacting the connectivity and nothing has worked. For example, enabled mDNS and IGMP Snooping on my AP but it didn't work.

If anyone can provide a solution or let me know what can I do further to narrow down my diagnosis that will be really helpful.

Thank you.