When you setup the doorbell, it uses the MAC address that's shown on the Device Information page.

I use that MAC address to assign a fixed IP to the device.
But after a while, it suddenly starts using another MAC address, even though the Device Information page remains unchanged:

So instead of 9c:8e
Why does it do that? Where is that other MAC address coming from?
Now, the app continues to work, and I can update my DHCP server to assign the IP address to that new MAC address.
But a bigger problem is that it doesn't let me watch the rtsp stream anymore, because it believes my password is wrong.
I've done a hard reset and gone through the complete setup again two times now, and it keeps doing this.
Both issues must be related, because I'm 100% sure my password is correct.