Blender 2.83, was sculpting and suddenly my smoothing brush stopped working I have no idea what happened, but when I try a stroke, a red line appears which hadn't appeared before and I'm still new to 2.8 so i have no idea what brush settings could have caused this.

This only affects the smooth brush.
In the Properties sidebar, go to Stroke &gt; Stabilize Stroke and turn it off.
Stabilize Stroke basically drags the &quot;actual&quot; brush behind your cursor when sculpting. This results in a red line indicating the distance the actual brush is from the cursor. I do believe this red line is resulting from Stabilize Stroke.