[Coco] Update on joystick fire button signal read failure: Left joystick port only.

[rjlilko at randing.ca]

I used a small basic program from "TRS-80 Models I,III and Color computing
interfacing Projects", Figure 13-3, to read the joystick ports. The right
joystick fire button signal  is read but not the left joystick fire button
signal. So it has to do with that circuit. Does anyone have a thought on
what could cause that in the circuit?