All workflows disappeared in the KNIME Explorer AAP 4.7.7

Second time I’m loosing all my workflows in the KNIME explorer. After changing the waorkspace the local workflow are not shown any more. In the workspace directory I can find them and all workflows that have been opened before and still have a tab on top can be opened. Seems to be just a problem of visualization, but for me the stop of my work.

Any Ideas?