Omitted question mark in quoted material How do I insert a question mark into a quotation that was omitted in the original material? For example, "Now we find that our land has unacceptable levels of contamination. Will it never stop[?]” Or "...Will it never stop"?
How about: "Now we find that our land has unacceptable levels of contamination. Will it never stop” [sic]. This indicates that the error was in the original and the quote is exact. 

See https://www.merriam-webster.com/dictionary/sic, the first definition here.