My LED Bulb II loses connection at 100%

So I tried what everyone else tried:
Turning off 5Ghz wifi and changing my DNS to Google’s (primary:, secondary
But this doesn’t change anything for me and my LED bulb still won’t connect.
In the past I also had some difficulty connecting but got it working once until it disconnected me a few weeks ago.
So now I hope someone has an idea what to do because I can’t return it anymore.

MI ID: 1899256543

I managed to connect to the Bulb by using the wifi-hotspot of another phone.
Also did a firmware update but this did not change anything.