Sidebar go up on material dialog open

Hi there,
I have an issue with sidebar… when i open a dialog at the bottom of the page, sidebar goes up until i close the dialog (as you can see in the attachment)
Can you help me?

Thank you,
Andrea.

Screenshot_1|690x337

Probably the material modal adds some classes to the body element and changes the height value.

Checked, but nothing… don’t know what to do.