Keyboard navigation keys inside the sp-textarea control don’t stay contained to the textarea. HOME and END will scroll the panel if it has a scrollbar. It can also scroll the main viewport. CTRL-SHIFT-arrow left and right moves a marquee if there is one. These are all common keystrokes users use to edit text and have consequences outside the sp-textarea control.
It would be great if this could be fixed, but in the meantime, is there any workaround for this?