Why are you trying to insert the sidebar into the builder’s content?
Could it be you’re trying to insert the Ultimate Posts Widget into the builder by using the sidebar widget (like I told you a few tickets ago)?
If so I’ll explain: I wrote that you should create a new sidebar (in Theme Options > Sidebars) specifically for the Ultimate Posts Widget widget. This way when inserting the sidebar into the builder page content it will only display the Ultimate Posts Widget widget.
Aside from that, you could set the page’s layout to be with a sidebar and then it will be displayed like you want.