040024 : A valid semivariogram model could not be calculated. Dataset has data in coincident locations, and the semivariogram model has a nugget of zero.
Coincident data with different values indicates measurement error. For semivariograms, the nugget is composed of microstructure and measurement error. Thus, if the dataset contains two or more different values for a single point, some measurement error exists, and the nugget cannot be zero.
Increase the nugget value of the semivariogram model so that measurement error can be included. Alternatively, choose a method to handle coincident values (for example, use the mean value).