Receiving packets with own MAC Address

[ASFP]

I currently receive this message on 2 of my 3 OpenWrt routers.

br-lan: received packet on lan1 with own address as source address (addr:12:34:56:78:9A:BC, vlan:5)

I have checked similar posts about this and all stated that there is a loop somewhere in the network. Which isn't the case in my network and also no device is spoofing the MAC addresses. I have the following network setup.

I have checked the Routers and all have the same MAC Address for the same interface. Now if I want to access the MGMT interface on one of my AccessPoints, I will connect via WiFi on the Unmanaged LAN interface, will be routed to the Main router inside the LAN VLAN (1), will then be routed back to the AccessPoint inside the MGMT VLAN (5). As it is intendend.

How do I get a package at one of the APs saying it has its own MAC? All the Ethernet Frames should be rewritten with the MAC address of the Main router when they get processed by it.

Can anyone help me with this?

FYI: I have this since I upgraded to 21.02.

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[ASFP]

After locking myself out of the 2 APs it turns out that it had some kind of problem in the switch configuration. I used the config from one AP for the other one during setup and it took the same MAC addresses????
After rolling back to a backup I went to Interface->Devices-> and reset all devices except for the br-lan. This resulted in it actually using its real MAC address.
The weird part being that the MAC address which was used by both of the APs isn't the same of any of them.
I don't know how this can happen. Seems very strange to me.