An error has been found. Two column elements below the slab are at the same location. Delete column element #a or #b.
This error occurs when you inadvertently draw a column at the same location twice, or copy and paste a column and do not change the Support Set (above or below).
To fix this error
Choose Layers > Mesh Input Layer > Standard Plan.
Choose View > Visible Objects ().
Check the Column numbers box.
Place the cursor at the appropriate column, double click and delete.
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