CSI/DSI attachments too dark

So following the manual pdf, I setup my Picam and Waveshare 4.3 DSI display correctly.
They both work, but they are dark as the night.

The Picam picture is barely visible, even when I light the area externally, the image brigthness does not improve.
Same with the TFT. Its working. Its just seems the background lighting is not working/powered properly.
But when I tap the tft, I can see Mainsail throwing the errors out like too low temp for extrusion.

I already checked and replaced the cables, of course.
both devices work as expected when connected to an original Pi 3B

So both devices CSI/DSI seem to have some kind of power issue, like missing a power line or not providing enough current on the existing lines.

Anyone got an idea?