This happens when someone puts extra path elements in a header, after something that should be a value.
For 360Giving, this happens when someone puts an extra colon where there shouldn't be: e.g. "Amount Awarded: website format", when only "Amount Awarded" is permitted (replacing the colon with another character e.g. a dash fixes this).
https://github.com/OpenDataServices/flatten-tool/issues/353
https://github.com/OpenDataServices/flatten-tool/issues/353#issuecomment-631514162