I just got a 5V Arduino Pro Micro, which I connected to an RC RX powered from the VCC and GND pins of the board.
However, whenever I do so and power on the board from a computer USB connection or a wall adapter USB connection, the board goes into an odd mode where the red RX and TX leds flash rapidly (~0.5s on and ~0.5s off) and USB serial ceases functionality. (presumably, because the MCU isn't on anymore)
If I remove the load and power the board again, everything works as normal.
This is an odd behavior, especially since I read online that the VCC pin is rated for ~150ma max and my device (FS-iA6b) isn't a very high power device, tested by me to draw 30-50ma max.
What is happening here? I haven't even connected the 5v signal pin yet!