UNO R3 + W5100 Ethernet shield - power/bootup problem

[otto001]

Hi,

this might be a little OT, cause it is not directly related to mysensors, so sorry.
But maybe someone knows this problem or even a solution.

I got some UNO R3 boards and W5100 ethernet shields on ali.
Uploaded some sketch and everything worked fine as long as I was using the USB cable connected to my pc.
But then I wanted to go in production and used different power sources:
A 9V adaptor connected to the power plug, even with a DC-DC module with voltage from 5V up to 9V, 5V directly to the USB port of the arduino, but nothing worked.
What the arduino does when I turn power on or connect it to the already plugged in power source: The power led is on and the TX LED is blinking several times. Until I press the reset button on the ethernet shield - then the arduino is booting the sketch and everything is fine.
Does anyone know this problem? Some hints would be really fine!

Cheers,

Pula