problem combinations values zero after new edit product

[m.voglino]

After creating a product combination I'm going to edit the impact on the price and weight of each one.

I realized that if I enter a second time to change even just one value, they all go back to 0 "zero".

So if I enter 3 combinations, change the weight and price impact values, save and return everything goes back to zero

PS version 1.7.2.1 but also occurs on 1.7.2.4