CDO (and other third party packages) may not have the correct GRIB tables to interpret some of the ERA5 variables in the GRIB files correctly. In the case of ERA5 accumulated parameters for example, this can lead to CDO printing an error message (such as "cgribexGetTsteptype: Time range indicator 130 unsupported, set to 0!"). It is advised that the ECMWF ecCodes package is used to interpret these data correctly.