Reply To: Master page, column gaps different

The recto and the verso are treated as separate pages so you have to make sure both of their settings are the same. In the Pages panel double-click the master-page name (A-Master or B-Master or any name label that it has), this will select both pages at once. Go into Layout ⟩ Margin and Columns, and in the dialog box make sure the margins, columns and gutter options are defined. So now both pages will have the same settings.