I'd observed this a couple of times before but couldn't reproduce it until now:

 

Create an item with this text (paste as single item, might want to lose the quotes):

 

 

"For up/down arrows:

    None: Focus Next / Previous item
    Shift: Select items
    Ctrl: Scroll view up / down
    Ctrl + Shift: Focus Next / Previous item + Scroll
    Alt: Move items Up / Down
    Shift + Alt: Focus Next / Previous sibling
    Shift + Alt + Ctrl: Focus Next / Previous sibling, add sibling if at end
 
The number of lines to scroll is set in Tools > Options > Grid"

 

 

 

What I did then was, in edit mode, use the mouse to highlight multiple lines (e.g. from "None" to "items" in the following line). Now press delete or backspace, then maybe move the mouse a little.

 

Voila. CPU load will skyrocket and the mouse cursor will start to flicker, constantly changing from the one used for editing back to the regular pointer.

 

If you press Escape to cancel edit mode, everything goes back to normal. Doing nothing, I think I've even experienced some crashes / permanent freezes, but not sure if it was the same issue.

 

I hope you can reproduce, Pierre.

 

Cheers and a happy new year!