A Weight /combinations Problem

[medalto]

Im struggling with configuring carriage according to weights .

there is a cutoff at 25 grams ( a card) and then up to 1kg.

other items are 100g

if i choose the card , it adds the correct postage . if i go back to the shop and add another item it still shows the card postage, not the larger item .

If i start with the larger item , it dispalye the correct postage for that item

 

My default weigth unit is Kg

 

the zone weight bands is also in Kg.

my item weight in theproduct config is currently 100g ( and 20g)

 

Do i need to go through all the items and change it all to 0.025 and 0.100 ( ?with  unit kg added )

 

or could it be something else ?