On a workboard, click on the pencil for a column and choose “Move Tasks to Project…”. Select a project and the list of columns will be the list from the current project and not the target project. Moving results in either an error or the task winding up in the wrong column of the target project.
This appears to be the result of commit 58e2fa0d47fd65028419752151337f9e2b546b2f which separated “Move Tasks to Column…” and “Move Tasks to Project…”. I believe line 110 of src/applications/project/controller/PhabricatorProjectBoardViewController.php should pass $dst_columns to mpull instead of $columns to correct this.