I think I remember you from the other thread. I realise what you mean now.
Funcom recently fixed some areas that were suspected to be used for undermesh (out of map) exploits. They did this by essentially expanding parts of the map.
I also lost many items at the boundary spillway;
P.s. It may be obvious, but Thralls return to the last location they were on guard. So if you only told it to stop following, it will teleport to its original guard location.
P.p.s. Thralls don’t need to be fed anymore.