Hi @bjornvandijkman,
You are probably hitting this issue which comes from this original discussion where you want to cache the results of a Dataframe that is being created from an uploaded file. Streamlit doesn’t know yet how to handle a file stream from its file uploader widget.
Until the issue is being solved natively by Streamlit, you can try to hash part of the uploaded file or use the more consuming solution of reading and hashing the entire file 
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