GroupBy provides incomplete sums

Hello,

I have a table with 3 columns. In one column I have several identical values and would like to have a sum of the values in another column for these values.

This should actually work with GrupBy.

From a table with 150,000 rows and 459 identical values in column B, the complete sum of the corresponding values from column C is not calculated, but only a part.

Have I overlooked a setting?

Manual aggregation is Sum.

I would be very pleased if you could suggest a solution