Screen Mirroring issues between iPhone and a specific Apple TV

So I've done some more troubleshooting:

• ⁠ATV and phone both on downstairs AP: can connect
• ⁠ATV on downstairs, phone on upstairs AP: can connect
• ⁠ATV on upstairs, phone on downstairs AP: can connect
• ⁠ATV and phone both on upstairs AP: cannot connect

All of these scenarios involve the iPhone connected to the Home VLAN and the ATV connected to the IoT VLAN.

But it seems the issue is specific to when both devices are connected to that specific AP upstairs. What issue could be causing that?

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So this is a weird one. My current set up is:

• 3 x Apple TV 4K (Two on WiFi, one hardwired)
• All Apple TVs are on the IoT VLAN
• Our cellphones are on the Home VLAN
• mDNS is allowed between the VLANs
• Traffic from Home is allowed to IoT and return traffic is allowed
• All Apple TVs are listed in the screen mirror selection menu
• Two of the Apple TVs allow screen mirroring just fine
• One Apple TV will only accept screen mirroring if the iPhone is on the IoT VLAN
• My MacBook Air can screen mirror from the Home VLAN to the suspect TV no issue
• I have already factory reset the Apple TV and that did not resolve the issue.
• AirPlay is on, access is set to everyone, peer-to-peer wireless is on

Any help would be greatly appreciated. I think this is a network issue, but I'm also going to seek out some Apple specific assistance as well.