It’s an overexposed area and it is only visible when Highlights reconstruction is set to “reconstruct in lch”. Although I am not sure if it’s visible with “reconstruct in color”. They are regular like a chain around the sun.
It’s not visible in RT.
Edit: they cannot be fixed with hot pixels.
I have never been confident in dt’s HR because it is unreliable and sometimes buggy. I use RT for that. Have you tried fiddling around with the WP (i.e., white point) or even WB 
to see if you can get the artifacts to go away?
Well actually I am not so much interested in getting rid of them, well yes that too, but I think it is just interesting, quite regular… what is the reason for it
never seen something similar before
how dirty is your lens/sensor?
these crosses looks suspiciously like one broken pixel (not so much like dirt). if they aren’t in fact broken (hot/cold) the code may run into numerical issues that drops one pixel to straight zero/negative? i’m not familiar with the current “LCh” code, maybe there is an edge case triggering somewhere?
Actually I must admit that I never really cleaned my sensor with a wet cleaning medium, I just try to keep it clean and blow the dust away when I see some. Some time ago I made a long exposure shooting with very small aperture and I did not see any dirt. So I think my sensor is clean.
But if this were dirt, the pixels would not be so regular, would they?
Same should apply to broken pixels. Must be a fascinating mathematical paradox?
Wouldn’t it be interesting to try to reproduce this?
you are right. If I switch white balance to daylight the dots go away. So this tells more about the genesis of the dots?
Yup. It seems that @hanatos is completelly right - it’s numerical edgecase. Probably reconstruction fails with WB coefficients you’ve set for edgecases looping values into negative or outright trimming them. This gets reconstructed wrong way and you see artifacts.
Thus your image might be a benchmark for reconstruction 
What is numerical edgecase? (Is it possible to explain this to a humanist?)
If I just double-click on any silder in the white balance module, the dots go away. So the actual white balance values are not changed.
Simplest? Hmm… Have you heard about pythagorean cup? If you fill it -it’s full. if you add to it a bit more, it drains till it’s empty. Same with some numerical values and it’s called overflow/wraparound.
That actually sounds like it’s processing pipeline artefact… weird.
