Web Item opening Fullscreen Dialog in system.space.sidebar/main-links

Hi,
I’m trying to place a web-item in the left space tool bar (location system.space.sidebar/main-links) to open a fullscreen addon dialog. Creating the item works fine, opening the dialog fails and I am redirected to a jira url or at least a Screen showing the jira logo at the top left menu.
If I place the web-item at another location such as system.header/left, the dialog opens as excepted.
Do you have any advise or hint how to fix this?
Thanks
Benjamin

    "webItems": [
      {
        "location": "system.space.sidebar/main-links",
        "weight": 200,
        "styleClasses": [
          "webitem",
          "system-present-webitem"
        ],
        "context": "addon",
        "target": {
          "type": "dialogmodule",
          "options": {
            "key": "my-dialog-module"
          }
        },
        "tooltip": {
          "value": "My Addon"
        },
        "icon": {
          "width": 16,
          "height": 16,
          "url": "/assets/my.svg"
        },
        "name": {
          "value": "My Addon"
        },
        "key": "my-space-tool"
      }
    ],
    "dialogs": [
      {
        "url": "/frontend",
        "options": {
          "size": "fullscreen",
          "chrome": false,
          "header": {
            "value": "My Dialog"
          }
        },
        "key": "my-dialog-module"
      }
    ]