Why is this corrupting my save for this file?

Everything works fine. When i click the button the code is executed and the progress bar updates. There is just something wrong when it come to saving. There must be a way to do what i am doing with out generating the save error. I know it is caused by the Asset_deathbox from persistent level but that is there only thing that allows the cast to work.


You can see in the above gif when I click the button (I am clicking the button between the pictures) it does what the code is supposed to do the only problem is when trying to save it. Please help me figure this out. The picture below is more info on the error. Thank you ahead of time!