Auto sizing curly brackets showing up in unassigned boxes

i have colored boxes on master pages, on edges edge of pages matches color of tabbed dividers section. today, i've been working on variations of file couple of weeks now, boxes contain right curly brackets span height , width of each box. each box still has content setting of unassigned, yet brackets persist. when change size of boxes, brackets distort match new box dimensions. need turned off , may recreate boxes, i'd know did can undo it. heck, can see use behaviour, want control when happens.

 

any idea of might have done cause this?

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