Droptarget intermitent problem

I’ve been trying to build a simple? drag & drop quiz & although it works sometimes - sometimes it doesn’t. (I’ve spent today looking a drag n drop tuts including the tut on this site)
The approach I’ve used seems the same as the mx tuts I’ve seen - button inside mc for drag & movie clip for the target. But it doesnt always work first time - sometimes after the drag & release the result is ‘wrong’ when it should be ‘correct’ After re-dragging the mc away releasing on a wrong target & dragging it back to the correct one & re-releasing it gets the right answer.
I’ve got several frames with a resistor in each which when clicked shows its resistance in a dynamic text box. then the user drags resistor to one of 6 boxes(Movie clips) & releases & result is stored in answer* variable. (where * is a number from 1-8)
I cant seem to figure out whats wrong. I tried altering sizes of target areas etc but it still only works right sometimes. Can anyone suggest where I screwed up?
TIA Scally
This is the script within the dragged mc:
onClipEvent (mouseDown) {
// when mc is pressed , drag it
on(press) {
// when mc is released stop dragging
on(release) {
// if the right shape , leave it there
if (this._droptarget == “/1percent”) {
_root.answer1=“1 megohm correct”;

		// if wrong target, 
			_root.answer1 = "1 megohm wrong";