Re error after KBPF3A mod to K3 RF board, 9V filter;Most likely you put the ground (red side of cap) to the wrong via.
The arrow in the instructions covers the picture.
The ground is the one out in the vast area farther away from the 9V via. (Not the short trace nearby).
(and why the ground on the cap is RED is unknown to me!)
Keith WE6R Elecraft K3 Tech.