I can say without a doubt after 4 seperate tests this doesn’t work for me. I built a bridge over the area that this occurs for me and didn’t matter what I built they fell through. even if it was two foundations high. the worse part is this is just a few steps from my base.
Now the advantage is of course is I know that spot is a line across the area … and it happens in the exact same spot ever time. Like there is an invisible wall/cliff. So if I build use the blocks in front as a base I could build a wheel of pain right there to solve the issue temporarily. there are three lines I know of for sure. I could map them out but Why… lol I suspect though if I did and showed them to a Funcom developer… they would go “Ohhhh I see what is happening.” because the lines are straight… and I suspect that they all intersect like a series of blocks/zones
I did do a quick map of two of the zones which basically totally block of camps from my base. I did end up building a wheel just on the good side of the line but a thrall can’t pass those lines for sure. I dotted places I’ve lost thralls.