Manamune gameplay resetting stacks bug

As i was playing ad malzahar, I bought a for my build . I began noticing that every time I died the stacks would reset back to 0 and i'd have to start all over. Then as the game progress and i go 8/14/21, every time i died it would reset. then another issue was that it never transformed into the . so when i finished the game i never got to that item. also it never seemed to give me any of the bonus ad its was supposed to give me from my mana. how to achieve this:

1. buy
2. die without finishing the stacks