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Deselect the Show widget borders checkbox when you edit and paste the code into the Custom HTML widget in Design Studio:
Ensure that the widget is the correct size in terms of the number of columns and rowscorrectly sized and that the height and width set in the Widget builder match those which are set in Design Studio. For example, if you’ve created a widget that is 6 columns wide in the Widget builder, ensure that the Custom HTML widget in Design Studio, where you are pasting the code, is also 6 columns wide:.
Try performing a hard refresh.
If the issue continues, please raise a ticket with Fuse Technical Support.