AIPlayer Transform returning 1.#QNAN after SetMoveDestination

I'm having a (somewhat intermittent) problem with AIPlayers vanishing and returning garbage on their gettransform calls. The AIPlayer is using a standard Torque-ship model: I've tried with Kork and Mr Box with the same results. Terrain is flat, set to squareSize of 8. Player models are a scale of 1 1 1.

Example of the getTransform call:

==>echo(2679.gettransform());
1.#QNAN 1.#QNAN 1.#QNAN 1.#QNAN 1.#QNAN 1.#QNAN 1.#QNAN

An AIPlayer will occassionally vanish from the visible scene when receiving a SetMoveDestination call. Sometimes I can go dozens, even fifty tests without a hitch. Other times, an AIPlayer will exhibit this behavior 2 out of 3 times. At first I thought they were dropping below terrain, but once I checked transform and found that they were not listed in a legitimate location (nor could setTransform calls bring them back) I tried to puzzle out what was happening.

The synopsis is thus: I have a custom walkpath system where the object determines a destination in world space and creates a simple route on an 8x8 grid to that point, walking only orthogonal directions. To simply the walkroute, it only creates a node on bends/intersections, so that it will walk in straight lines where possible.

The nodes are simply ordered pairs plus getTerrainHeight() stored as variables on the AIplayer as thus:

node0 = "116.5 -103 0.02"
node1 = "111.5 -103 0.02"

The AI uses the onReachDestination call back to check its point on the path, increment to the next node using lastNode and currentNode to tell which portion of the path its working on and when its finished. When the AI players vanish, they seem to do so on the first SetMoveDestination call (i.e., to Node[0]) on the path. I don't believe I've witnessed a situation where they've vanished at other steps along the path.

The game used to lag tremendously when this happened...Using profiler I tracked that to a rezoning problem where the game would get stuck on SceneGraph_rezoneObject (using 90%+ processor time). Removing .difs in the scene seems to have stopped the rezone problem when the AI vanishes, but not the vanish problem itself.

My next step is to go back to a Debug build and try to dig deeper into this. Any suggestions where to start?

Example of the onReachDestination/walkroute function:

function AIEnemy::onReachDestination(%this,%obj)
{
if (%obj.followPath == 1)
	{ // We're following a walkroute right now
	if (%obj.lastNode == %obj.currentNode)
		{
		%obj.followPath = false; // We're done with the path
                echo(%obj SPC "done following path: Stopped at" SPC %obj.getPosition() SPC "for node" SPC %obj.currentNode);			
		}
	else if (%obj.lastNode > %obj.currentNode)
		{
		%obj.currentNode = %obj.currentNode+1;
		%obj.setMoveDestination(%obj.node[%obj.currentNode], true);
		echo(%obj SPC "following path: Moving to" SPC %obj.getMoveDestination() SPC "for node" SPC %obj.currentNode);
		}
	else
		echo("AIEnemy::followWalkRoute error - returned invalid node");				
	}
}