The spell does not support multiple uses (aka it's not MUI or MPI).
Also, every 0.01 second is too fast: use every 0.03 or 0.04 second instead.
I believe
this spell basically does the same thing by the way (and I've seen other variations of this spell, including one I created myself).
Another thing: I believe you do have leaks.
At the end, you do Set ManaFormLoc[1] = ManaFormLoc[3] ==> The original ManaFormLoc[1] will leak as you never removed the point (as long as a variable is not changed, it will not leak - but you changed the variable, thus creating a leak).
And you created a group in the loop but never removed that group either (aside from the end), creating another leak.
Edit: further info on the leaks.
So in the init trigger you set ManaFormLoc[1] to something, let's say Location(0., 0.) (coordinates).
The loop will set ManaFormLoc[3] to (let's say) Location(0., 1.).
Then at the end, you set ManaFormLoc[1] to Location(0., 1.), while the original location Location(0., 0.) was never removed and warcraft will keep remembering it.
The same goes for the unit group which is never removed in the loop while the variable does change.
What? O_O
I honestly didn't understand a word of this.