I disassembled the Duo Pop. Following the traces on the controller board, I noticed that the pins between the IR receivers are connected. I replicated the traces with wires.
I looked up which resistor Adafruit recommends using with LEDs. They have an example with the QT Py RP2040 using 470 ohms. The closest I have is 430 ohms. It took me a bit to figure out the markings, K43 J∆, on the resistor. I got them in Russia and forgot to mark their bag. I had to look up what the tolerance, J, was. They are 430 ohms with a tolerance of ±5. My multi-meter says they are about 426 ohms. I replaced the LED- wire with the 430 ohms resistor.