Hi.
I have a used Mikrotik and this is the first time I put my hands on and I am really enjoying!
I notice a strange behaviour when power up. If I remove the power cord and re insert it, if there are eth plugged on the port (obviously) the router seems stuck (blue power led and weak green light on eth2).
If I power it up without any eth plugged, it starts normally.
What should I do?
Thanks

Is that RB5009 by accident a POE version and is that ethernet connection feeding POE (but not enough power) ?

mmm is the poe version, but there is not any poe on the cables.
I read on another 3d that the last firmware erase the bootloader. The behaviour is the same but I found the temporary solution to disconnect all the cable.
In the other 3d they found a solution with an hardware tool to flash it. Can I do the same without the hardware since my router is booting without any cable?

this is the 3d
viewtopic.php?t=216738

It is not due to "latest firmware".

That happened to people that updated the bootloader with a specific "universal" bootloader update (that later came out as being "not-so-universal").
That particular file never was part of the "normal" update/upgrade.

If you did not make that particular update (actually intended only for some specific devices that showed a specific error message) the reason why you have that behaviour may be different.

Post some details on which upgrades/updates you made and when the issue came out first time.

Try checking the firmware version the device shows and post that info, see:
viewtopic.php?t=175182

With these info - maybe - someone could give some advice on the steps to try.

I don't remeber from which version I came because it's the first time i seriously configure it, was in a box ready for the new home, but this behaviour was not there the first time I try, maybe 1 year ago.
I remeber that I update from the packages menu of the winbox, like a wizard. picked tha version on the screen
Btw this is the screen I got
hope you can help me.
thanks

Press the "Upgrade" button and afterwards (it will show a text message in red letters saying you can reboot) reboot the device. These steps will upgrade the firmware (and there are a couple of firmware changes between the running and available version).