I just encountered this problem today, so I'll upload My problem file. How this problem started for me is when I used one of the RTPModles to speed up my manual ReTopo, also, the Split Tool in the ReTopo Room started crates undeletable seams after i imported the RTPModle.
https://www.dropbox.com/s/it8do693uctu4o4/Cleaver.7z?dl=0