\uD83E\uDD14 Problem
When trying to export a project, it fails with the following error:
javax.xml.bind.MarshalException - with linked exception:
[org.xml.sax.SAXParseException; lineNumber: 0; columnNumber: 0;
cvc-complex-type.2.4.a:
Invalid content was found starting with element 'daysInColumnShown'. One of '{column}' is expected.]
The problem is that there is a board that has no columns configured for it. While the XML schema is expecting at least one element of type column for every board.
\uD83C\uDF31 Solution
Identify such boards and configure them to have at least one column.