I’ve had this issue a number of times myself, and know some of my clanmates have also experienced it.
I have a base near Scuttler’s shortcut. I often go to New Asgarth or The Black Galleon to find named / high level artisans to capture as thralls. Sometimes, I forget to repair the binding first and it breaks en route back to my base. If I switch to a new binding and attempt to re-bind the (still unconscious) NPC they have a tendency of bugging out and disappearing through the floor. It doesn’t happen every time, but enough that I’ve lost several high-level NPCs this way which is very frustrating after going to all the trouble of finding one I want and getting it most of the way home!
I lost three T4 cos of suddenly vanishing thralls…
Two of them just dissapeard while they where bound and I was looking around with the “V”-Key and after hours of farming I finaly found the Legendary Armor and while I draged him to my base I had a client crash “Fatal Error” and when I came back he was poof… VERY annyoing…
I repaired bindings while attached to a taskmaster. Everything was fine until I tried to re-attach the fiber bindings. Then the task master flew through the air and dove into the sand. Disappearing forever.