Pixinsight Dynamic Background extraction adds Color artifacts [Deep Sky] Processing techniques · Jens · ... · 4 · 243 · 2

DBE with very few sample points might be prone to err but you can always re-balance everything back to normal with BackgroundNeutralization and ColorCalibration afterward. Advise to avoid it in images with very little background such is this case. At most use linear ABE to correct for major gradients.

I think you have other issues at play.  Look at those two images - the color artifacts in the first image are at an angle at the bottom of the image.  But, in the DBE image you posted, the lines are straight up and down (more or less).  It does not look like they line up.  

I agree with what is said above - it's very hard to impossible to a good background model on an image that is all nebula.  Most just skip this step.

Is the DBE image you posted linear or an STF stretch?  If it's STF, you can choose 'use 24bit' and it should look much better.  If it's linear, you can increase the smoothing factor, which should help.

Another possible issue is:  if the thing that needs to be extracted is from a flat-based error/artifact then you MUST use division instead of subtraction.  If it's sky gradient, use subtraction.  Your issue looks like a division problem. 

These days, I'm often using the very excellent and free AI-based program, Graxpert (graxpert.com) instead of DBE.  It plugs into PI and gives one-click AI based gradient extraction - give it a try and see it if works better for you.