Shift button plus I or K causes all text to highlight

Hi, When I'm typing and I do a capital I or K it highlights all the text from behind the cursor and then of course the next button I press deletes it all because it's highlighted. Also happens sometimes but not all with both shift buttons. It seems like a bug as there's inconsistencies for example it's been happening within this paragraph but is not happening in the title paragraph. I have encountered it in mail and pages plus here. Please help as this makes the computer unusable for me. It's a recent thing and not sure if it's last update related.