Double value after incremental refresh

Hi there,

I have a strange problem that since incremental refreshing the amount of some values have doubled.

The incremental refresh is scheduled like this :

Now suddenly the value has doubled form this: 

to this

As you can see the value on the left is still at 733, but the value on the right has doubled? 

It is only with a some values, most of the values stay correct.

I noticed that the it only doubles the amount where there is only one day behind it.

So I get sales data for one shop once a month, lets say on the first of each month.

And now the shop where there is only one date behind it, that amount gets doubles.

Do you know how to avoid this?

Thanks!