MAC Address changed after flash

My mobile: Xiaomi Mi Mix2. First flashed the stock MIUI version (10.2.2.0) and after that "clean flashed" the /e/ ROM (Android 8.1.0). (Format data, wipe cache/system, flash).

After rebooting I detected that the Wifi MAC Address was changed (last letter changed from "c" to "d"). This made my Wifi connection at work non-functional anymore (MAC address registration enabled).

Can this be resolved? At XDA I found a possible hint ... https://forum.xda-developers.com/showthread.php?t=2121151

Tha app "Change My MAC - Spoof Wifi MAC – Apps on Google Play" made it possible to change back my MAC address and I proved the connection was working again. Since it was a temporary solution (with too many trackers) I found this not good enough as a solution.