Mouse Lag with External Display
I got an external 4K monitor to use as a secondary monitor for my 27" iMac. Since hooking up the secondary monitor my mouse will lag on the iMac. How do I fix this issue.
iMac 27" 5K, macOS 10.14
The mouse is using one of those little dongles and it is possible/likely that the display is emitting interference. Try moving the dongle. Back when I was using a Microsoft mouse with a dongle I couldn't get it to work reliably when it was connected to the back of my computer so I put it on my hub which solved the problem.