I'm trying to make a submmit with an .csv or a .xls generated with pandas

- when I submitt the submit.csv, it merges the headers cells "ID" and "transcript" together and when I download it, for some reason the submit.csv now is submit.xls

- Then I tried making a solution_df.to_excel("submit.xls"), but it throws the error "unknown error: invalid byte sequence in UTF-8"

I've tried with pd.to_excel(encode=UTF-8) and still throws the same error.

I'm working on local