Open any contract -> Go to Terms Tab -> Select any existing group -> Double-Click on any dimension field (Rights Type, Territories, Platforms / Formats, Languages / Services)
Although manually selected (entire line/grid), only items from the first column remain selected
I've checked your issue and provide next screen and text from our documentation
The <o:columns> tag does not have the id or rendered attributes. However, you can specify the identifier and a flag that indicates whether or not the column is visible for each dynamic column using the columnId and columnRendered attributes of the <o:columns> tag, respectively. These attributes should be specified as value-binding expressions that refer to identifier or a flag indicating whether column is visible for each dynamic column. You can use a column data variable specified in the var attribute in the expression for these attributes. Please note that column identifiers evaluated for columns inside the <o:columns> tag are used in the same way as id attributes of ordinary <o:column> tags, so the identifiers evaluated using this expression should be unique in bounds of the containing DataTable.
Also, you try to change your checkbox, but all your checkbox have identical id