Whenever I navigate away from the dashboard Sortable.js throws an error because when destroying the element is undefined. It basically tries to destroys what doesn't exist anymore and throws a null references.
I've tracked the error down: The columns containing the widgets get destroyed first, right after them do the widgets get destroyed. But they don't exist anymore as the containing column already was destroyed.
Is that a known error or did I screw up something?

The error occurs in column.js line 147, $element.on('$destroy', ...

Fixing it means adding following code before line 148: If(!sortable.el) return;