Finally, I found a solution to circumvent this annoying bug.
You have to create a new profile and put the first autosave file for chapter 8 in it. You have to find the folder that contains a savegameinfo file where the 3rd line reads: o.Type = "AutoNewLevel". I guess this resets the artifact spawning.
Maybe it's sufficient to put this line in a newer savegameinfo file. Go and test it I'm now going to continue my second round of NVLC.
oops, forgot something: You have also to change the line which refers to your profile name, e.g.o.Profile = "default" goes to o.Profile = "xyz", otherwise it will not work.