Plasmashellはもう起動しません。

何らかの理由で、ボックスにログインしてプラズマを実行しようとしたときにアプリを起動しましたが、壁紙やパネルが表示されず、右クリックしても状況に応じたメニューが表示されません。 Plasshellを手動で起動しようとすると、次のようになります。

$ plasmashell 
kf.plasma.quick: Applet preload policy set to 1
Qt WebEngine seems to be initialized from a plugin. Please set Qt::AA_ShareOpenGLContexts using QCoreApplication::setAttribute before constructing QGuiApplication.
Attribute Qt::AA_EnableHighDpiScaling must be set before QCoreApplication is created.
Attribute Qt::AA_EnableHighDpiScaling must be set before QCoreApplication is created.
Attribute Qt::AA_EnableHighDpiScaling must be set before QCoreApplication is created.
trying to show an empty dialog
file:///usr/share/plasma/shells/org.kde.plasma.desktop/contents/views/Desktop.qml:146:19: QML Loader: Binding loop detected for property "height"
file:///usr/share/plasma/shells/org.kde.plasma.desktop/contents/views/Desktop.qml:146:19: QML Loader: Binding loop detected for property "height"
trying to show an empty dialog
file:///usr/share/plasma/shells/org.kde.plasma.desktop/contents/views/Desktop.qml:146:19: QML Loader: Binding loop detected for property "height"
file:///usr/share/plasma/shells/org.kde.plasma.desktop/contents/views/Desktop.qml:146:19: QML Loader: Binding loop detected for property "height"
terminate called after throwing an instance of 'CppUtilities::ConversionException'
  what():  unexpected "-" after day
KCrash: Attempting to start /usr/bin/plasmashell
KCrash: crashing... crashRecursionCounter = 2
KCrash: Application Name = plasmashell path = /usr/bin pid = 4024
KCrash: Arguments: /usr/bin/plasmashell 
kf.plasma.quick: Applet preload policy set to 1
Qt WebEngine seems to be initialized from a plugin. Please set Qt::AA_ShareOpenGLContexts using QCoreApplication::setAttribute before constructing QGuiApplication.
Attribute Qt::AA_EnableHighDpiScaling must be set before QCoreApplication is created.
Attribute Qt::AA_EnableHighDpiScaling must be set before QCoreApplication is created.
Attribute Qt::AA_EnableHighDpiScaling must be set before QCoreApplication is created.
fish: Job 1, 'plasmashell' terminated by signal SIGABRT (Abort)
ron@DesktopRon ~ [SIGABRT]> trying to show an empty dialog
file:///usr/share/plasma/shells/org.kde.plasma.desktop/contents/views/Desktop.qml:146:19: QML Loader: Binding loop detected for property "height"
file:///usr/share/plasma/shells/org.kde.plasma.desktop/contents/views/Desktop.qml:146:19: QML Loader: Binding loop detected for property "height"
trying to show an empty dialog
file:///usr/share/plasma/shells/org.kde.plasma.desktop/contents/views/Desktop.qml:146:19: QML Loader: Binding loop detected for property "height"
file:///usr/share/plasma/shells/org.kde.plasma.desktop/contents/views/Desktop.qml:146:19: QML Loader: Binding loop detected for property "height"
terminate called after throwing an instance of 'CppUtilities::ConversionException'
  what():  unexpected "-" after day

これは間違いなく悪いようです。

terminate called after throwing an instance of 'CppUtilities::ConversionException'
  what():  unexpected "-" after day

しかし、この問題を解決できませんでした。誰でも助けることができますか？