Multi-Select Matrix within a Panel - Matrix Borders are rendered incorrectly

[JaneSjs]

To reproduce the issue, navigate to https://surveyjs.io/create-free-survey. Add a panel and drop a Multi-Select Matrix within the panel. Set a Static survey width mode.

{
  "pages": [
    {
      "name": "page1",
      "elements": [
        {
          "type": "panel",
          "name": "panel1",
          "elements": [
            {
              "type": "matrixdropdown",
              "name": "question1",
              "columns": [
                {
                  "name": "Column 1"
                },
                {
                  "name": "Column 2"
                },
                {
                  "name": "Column 3"
                }
              ],
              "choices": [
                1,
                2,
                3,
                4,
                5
              ],
              "rows": [
                "Row 1",
                "Row 2"
              ]
            }
          ]
        }
      ]
    }
  ],
  "widthMode": "static"
}

Select a matrix and you'll see the borders are rendered incorrectly: