Brightness much too high / no more colors

2 (wonderful...) days my setup was working perfect. Thanks Devs!

Now i got a strange problem: the brightness seems to be much to high. That results in only white light, but no more colors.
When i reduce the luminance in Hypercon to 1 (sat remains 2), the colors are normal again. With 2 / 2, only white light.
The same goes for the color SSH-wheel in Hypercon: if i reduce the brightness there (while keeping 2/2 in Page 1), there is color again. With the normal setting in the wheel, i get only white light, no more color.
Of course meanwhile i created a json with lum1/sat2. But that has no effect: i have to manually reduce lum to 1 again in Hypercon manually to get colors,

How to fix this? Already updated Hyperion without success.

Any Help in this case? The problem still occures from time to time. After a night of shutdown its always gone. A reboot is not enough, a short shutdown too. It has to be some hours.