This just started happening recently on my laptop but not desktop, so I can't tell if it's some setting I enabled or something wrong with this specific computer.

Basically the scrolling using the down arrow has completely messed up on me. On PDF pages, pressing the up or down arrow will skip a whole page similar to the action of the left and right arrows, when it used to just scroll a bit of the page and was actually somewhat useful for reading. On any web pages, a blinking line shows up similar to the one used for any text entry, and that is all that moves when I scroll using up/down arrows. This means that the page either goes at the speed of single lines of text, or if there is a break in the text box it will sometimes skip a huge amount.