Item creation problem

Version 1.5.2

I place an item in the world with this method

%obj = new Item() {
canSaveDynamicFields = "1";
position = %pos;
rotation = "1 0 0 0";
scale = "1 1 1";
collidable = "0";
dataBlock = %block; << same as healthkit but different graphic
static = false;
rotate = false;
};

the %pos z is set up so that the object is half burried in the landscape. I use this to create 20 or so items for the mission. Creating and placing the items works fine.

Problem:
about once a second the object moves up a fraction of it's size and after about 10 to 20 seconds the object is floating above the surface of the land. I need for the item to stay where I put it.

I create the item using the in game editor and this does not happen.

Any Help ?