I have this PCB where I placed my Arduino. The RX and TX pin are connected to another component via PCB traces and female headers. I have not connected the component to the PCB so these pins are "open" (I have checked the PCB traces to make sure they connect directly to just a female headers pins on which I will place the other component). For some reason the upload won't work until I remove the Arduino from the PCB and then upload.
What is happening here? Why isn't the code uploading when the RX and TX pin are "open"/not connected to some component?