I use an iMac running High Sierra 10.13.6. I use the command line a lot and recently its developed a problem. I would use the left or right arrow key to move the terminal cursor along a previous command or line. If I made a mistake in a long line I was typing on the command line I would hold down the left arrow key and the cursor would quickly move along the line until I got to where the mistake was. That has stopped happening. Holding down the arrow key takes a second or more to move a single space. Continuing to hold it down is just too slow. It's much faster now to just repeatedly tap the arrow string. This is very frustrating and time-consuming. Does anyone know what happened? The arrow keys used to work fine. I've tried restarting but that hasn't helped. This also happens in text windows and other applications.