Question about Xiaomi Mi Smart Compact 120

since the last update the wifi stutters brutally. zattoo doesn't work at all anymore, netflix moderately. there are several forums where the problem is also discussed, unfortunately i only understand a lot or the xiaomi answer is to check the wifi for errors. does anyone know the problem as well? can you restore the fabeik version of android without doing an update right away? because that's all it took...