llMoveToTarget problems

I have a physical object with a sensor that detects a location, then issues an llMoveToTarget to make the object move to that location. Simple enough, but here's the problem: Many times, the object won't move. If you hold down your mouse on the object, the object moves, but when you let go, it snaps back to it's original position.

Now I have determined through help from others that the SL client won't update an object's position unless the move is significant, and adding an llSetForce to the move should help. Well it did help a bit, BUT it is still not 100%. It sporadically fails.

Any other ideas why this might be happening or how to fix it?

This happens to me all the time with a hover script I've fixed up.
Whats odd is that one ship I have in my inventory has no problems at all while an exact copy does. The only difference is I took the ship, the one that is all screwed up, and put it in my inventory after I had test driven the thing. So I make it a point to keep two copies of the same version handy. One to test and the other to edit.
So far we havn't had the problem on fresh copies of the "unsued" ships. Unless they are eventually taken back into inventory and rezed too many times.
I don't know why this would matter, and it might just be a fluke that it hasn't happend on the "unused" projects, but is seems like something is going on for sure.
Basically I wanted a ship to halt on command. The version with the problem acts more like a slingshot and flings back and forth around that halt position.
The other version works fine.
So after reading all that I'll simply say I have no idea.

Post the code involved and we can help you better.
Most of the time, with an llMoveToTarget, if it snaps back into place you're probably setting it to move to it's starting point. Then when you drag the prim it pops back into place after you let go.

Check the vector position of your first llMoveToTarget.
If you still have problems, post the code and we can take a look.