volume problem with Volumio v 2.555

Hi,
After installing the dedicated Volumio v 2.555, for Raspdac Mini, I found that volume management is not optimal. In the interface, it is parameterized to be increased or decreased by default with a step of 5. However, when I increase or decrease the volume, it varies with the first support with a step of 3 and not of 5. I hadn’t observed this behavior on the Volumio v 2.452. Could you tell me how to fix it on the v 2.555 ?
Regards.

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Frédéric