MAC Address changing after firmware update!

I noticed that the MAC Address of the printer changes after a firmware update! Why?

We are not able to give the printer a static IP-address via settings, so we have to change router-settings to make sure the printer is always on the same IP-address! But when the MAC-address changes I have to change the router-settings again!

Come on Creality, stop with this nonsense… make it possible to set static IP-address on printer (like it is possible on all other devices connected to LAN)…