I'm trying to program my NodeMCU ESP8266 ESP-12E module with AT commands. However, whenever I try and flash to my ESP8266 using ESPTool, I get a 3-run stub fail error. Can anyone tell me why I get this error and how to fix it? I have my suspicions that it might be the fact that I haven't pulled any of the pins, but I've been told that GPIO0, GPIO2, GPIO15, and CH_PD are all already pulled to the proper positions by default. If that may be the reason behind this error, could someone explain to me how exactly I should pull the pins, whether it be with a circuit or through code? If it helps, I'm trying to follow along with this resource. The only thing the ESP is connected to is the computer with USB.