Select the Dragonfly and find the script that starts with when flag clicked.

Drag an if inside the forever block. The blocks inside the forever will move inside the if.

when flag clicked
set size to [25] %
forever
+if < > then
start sound [Wings v]
point towards (mouse-pointer v)
move [5] steps
end
end

Then drag a not block into the if and a touching (mouse-pointer) inside that.

when flag clicked
set size to [25] %
forever
+if <not <touching [mouse-pointer v] ?> > then
start sound [Wings v]
point towards (mouse-pointer v)
move [5] steps
end
end

Test: Check that the glitch is fixed, and the Dragonfly only moves when it is not touching (mouse-pointer).

Try a different condition that makes the dragonfly move when it is far enough from the mouse-pointer:

<(distance to [mouse-pointer v]) > [50]>