My playhead in the timeline won't scrub, only jumps to the point where the mouse click is released.

I'm on CC 14.5.0 (build51)

iMac (Retina 5K, 27-inch, 2017)

CPU 4.2 GHz Intel Core i7

64 GB 2400 MHz DDR4

Radeon Pro 580 8 GB

Out of nowhere I have started experiencing some very strange behavior with the playhead and also the effects values in the effects monitor. When I grab the playhead to move it on the timeline it sticks and won't scrub, it then jumps to wherever I release the mouse click. The effects values usually increase or decrease when I drag then left or right but this no longer works. Any ideas why this is happening?