Spearzon Takedown stacks don't refresh the way I believe it's intended. At 5 stacks, hitting again does not refresh ALL 5 stacks, only one at a time.
This can be tested by getting 5 stacks, then not using takedown again until about 10 seconds have passed, and then attacking with it just once. You should stay at max stacks for 12 more seconds, but you lose a stack after about 2 seconds has passed (which would be your second gained stack wearing off).