Unifi APs set to DHCP on a VLAN and receive DHCP addresses on Guest Network (different VLAN) - but show correct IP in the UNCK controller?

I am having a strange issue where our Unifi APs (around 70 total) which are set to VLAN 10 pickup a DHCP address on our open Guest network with captive portal (VLAN 20) on our MS Server 2019 DHCP server. There is a SonicWall as the NGFW that is being used for VLANs assignment and DHCP relay. For some reason, the guest network scope on the DHCP server is the only one that keeps assigning IPs to the APs.

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On VLAN 10, I have reservations set for the APs. No other device is assigned an IP cross VLAN like this.

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I have tried recreating the networks, recreating the scope, ensuring that the Guest network VLAN is correct. The APs show the correct VLAN DHCP assignments in the controller and I can verify with a ping/ssh.

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I am going to add a Deny rule on VLAN 20/Guest network for the APs, but curious as to why this may be occurring.

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Thanks for any thoughts on this..