Thanks a lot for the detailed report. And no worries, I understood what you meant^^
Yes eternal parts shouldn't be removed, those are definitely bugs and I will look into them. For the fenrir extra fur part I think it happens because that part is a bit different made then the others. Will look into all of these.
The suggested fr the tail is also very interessting. Might be able to do that in the future. As for the curse parts. I felt them ignoring eternal parts would make more sense or else taking them would be no risk in taking the artefact. This might change in the future, currently I am not sure, what would be better.