1) The xls import fails (see output below), e.g. due to a non-convertible field (e.g. I tried to assign my running time to "Duration". It worked for fields specified in minutes, but it broke for fields specified as hh:mm:ss. Or when I forget to remove the header, it fails to assign the file size: the import aborts because it couldn't convert "Filesize" to a number.
Btw, what is the unit of "Duration"? Seconds? Minutes? it should assume Minutes, not seconds, by default.
I think, it should also recognize the "(h)h:mm:ss" format.
2) The import also failed for empty fields that needed conversion (e.g. I don't have duration entries in every field)
The expected behaviour in both cases would be, that Import leaves this one field empty and continue with the remaining fields in this entry. But instead, it aborts and throws an Exception.