Hey @Luis… I love how that little device is looking now, it looks so badass!
It’s very odd that the UI PCB is affecting your GPS though, it definitely shouldn’t be! As Ryan and CAProjects have said, the USB on the UI PCB is just running straight from the USB hub inside the pi-top, which connects directly to the raspberry pi, so there’s no USB-to-UART or anything like that. The rest of the board is basically just a breakout board, with little or no electronics on it. I’ve double checked my schematic and the UART pins (GPIO 14 & 15) are only connected to the pads on the 40 pin headers (the solder pads, and the bottom-entry header). Could there be some kind of electrical short on your board that’s interfering with pins 14 or 15? If this were a higher baud rate / frequency I might also have suggested that the added electrical ‘stub’ that’s created by adding the board could be creating high-speed signal reflection problems, but this can’t be a problem for such low frequencies.