Download fails when asking more than one day

[fjmachin]

Dear Rob,
thanks a lot for developing this toolbox. I installed it a couple of days ago and I'm trying to download a time series from a delimited area. Everything seems to be working fine when I ask for more than one year and also more than one month, but it fails when I ask more than one day. I provide below the options included in both cases.

This one asks for only one day and works, downloading a file with some 500 Kb:
datasetName ="reanalysis-era5-single-levels";

datasetOptions.variable = ["10m_u_component_of_wind", "10m_v_component_of_wind", "surface_sensible_heat_flux"];
datasetOptions.year = ["2000","2001"];
datasetOptions.month = ["01", "02", "03", "04", "05", "06", "07", "08", "09", "10", "11", "12"];
datasetOptions.day = ["01"];%, "02"];%, "03", "04", "05", "06", "07", "08", "09", "10", "11", "12", "13", "14", "15", "16", "17", "18", "19", "20", "21", "22", "23", "24", "25", "26", "27", "28", "29", "30", "31"];
datasetOptions.time = ["00:00"];
datasetOptions.area = ["29.5", "-16", "28.5", "-15"];
datasetOptions.format = "nc";

However, when the datesetOptions.day is modified to include more than one day (datasetOptions.day = ["01","02"]), it just fails and provides the next error message:

Mars server task finished in error; UserError: Duplicate value for month: 2000-01 [mars];
Error code is -2; Request failed; Some errors reported (last error -2)

Could you help on this?

By the way, despite I request the file to be nc, it only downloads it as a grib file...

I really would appreciate any help you might provide on this.

With best regards,
Francisco Machín.