I am using Photoshop 2019 CC, Wacom Intuos Pro M and Windows 10 (Windows 10 updates are run whenever offered). I have taken a Google road map and loaded it into Photoshop. I am using the brush tool to draw lines on the roads tracing my trip route. When I use the mouse I have no problem drawing lines anywhere on the map. When I use the Wacom pen I have no problem drawing lines anywhere except where I try to start on a road line. When I start on a road line, a circle appears around the pressure point and a brush tool menu opens and I can't draw a line. If I double tap on the line, then the menu doesn't open and I can draw on the road line. This is driving me nuts. Does anyone know what causes this problem?