I have made some tests on my side. It has the same issue as yours.
As the pic shown, the value of row 23, 24 25 are same.
So when you enter the last 'DATUM' value in the 'Key value' field to update the row 25, but actually, the flow is get the row 23 to update.
As you can see, you need use the 'Key column' and 'Key value' to get the specific row in the 'Update a row' action .

So if there are several same rows, it will update the top one.
So I am afraid you need create another column here to enter different value to distinguish each row.
Best Regards,
Community Support Team _ Zhongys
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Hi @RayRay ,