I see this bug with the WinForms control (version 5.0.37)

Using Alt+Tab to change the active window, turning on the zoom selection mode but does not turn it off because the window looses focus and never gets the Alt KeyUp event. When the user returns back to the original window, it stays in the selection mode and instead of dragging the chart using mouse, it draws the red zoom selection rectangle.

Temporary Fix

Before this bug is fixed in the library, one can use the following hack to simulate 'Alt' key up event when the window is re-activated:

private void Form1_Activated(object sender, EventArgs e) {
    // Hack: send Alt key up event to turn off the selection mode
    winFormsPlot.Interaction.KeyUp(ScottPlot.Control.Key.Alt);
}