Escort GT Stop Light - Voltage Drop or Bad Ground?

I have one of those old (c. 1990) graphic displays on the center console. Whenever I step on the brakes or signal a right turn the red
LED lights up. I swapped out the module with one I picked out of a junkyard with the same results.
All the lights work. I've tested I think all of the power and graphic display signal wires in the console and dash but have not detected any voltage drop anywhere, even into the hatch area.
What I have noted however is a slight difference in the ground wires leading from the light sockets back to the hatch body ground.
The brown wires (hot) to both lights register the same 0.10 volts (engine off) with both lights on. The graphic display signal wires both register 10.6 volts. The ground wire on the right side (the one with the problem) registers 0.20 volts and the left side registers 0.16 volts.
Could it be a bad ground causing too much resistance? Not exactly sure what the problem is that makes the red warning LED light up.
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