Whilst trying to copy and move a toolbox icon in the top line the auto save put a red cross in the whole toolbox line and removed all the icons !
As I move the cursor over where the icon was it shows up , then move the cursor back into the drawing windows the red cross removes all the buttons!
It’s a white back ground with a red line crossing from corner to corner. and no Buttons.
After closing Rhino6, then restarting all is back to normal.