I believe that kill zones override safety zones. Check to see if you have an extra killzone placed accidentally.
Also check where the piece is phased into, as some parts phased deep into natural terrain exhibit strange problems, ie: parts becoming invisible and unable to be picked up when phased into the mountain on the island too far. Another theory is that the part could be set to fixed and is moving at super fast speeds to try to free itself, but this seems unlikely. The kill zone thing seems most likely.
Is the wall phased into a premade structure? Walls phased into premade structures sometimes act as killzones.
Really? Put your map and a film clip of the problem on your fileshare and I can look at it for you. I could not possibly suggest what is happening until I look at both.
The problem is the Safe Zone. Simply put, dont use them. Safe Zones are opposite to Kill Zones whereas if you venture outside of them, you die. You can test this simply by removing all the Safe Zones on your map. Instead, wall your map in with Soft Kill Zones, and further out (or more problematic areas) use Hard Kill Zones.
I recommend deleting all kill zones and safe zones and then repeating the test. If you still die, then relocate or adjust the object.
Kinda bad if it does. Anyway, i'll try deleting all kill & safe zones and see if it still doesn't work. If it still ****s up, i'll post it in my fileshare.