I've had several RB3011 that have experienced the port flapping on 1-5 but I have one unit that wouldn't finish booting up.
After connecting to console it said demo license expired and to reinstall routeros.
I also noticed it said boot loader had crc error and using backup boot loader. No matter what you select no options are saved in the boot menu.
NetInstall it gets IP address but it never shows up in list to reinstall software. (Only way to get it to boot to NetInstall is holding down reset but it never shows up on computer)
I finally formatted NAND and that didn't help either.
I tried sending firmware but not sure if that was completed successfully. Also it was 3.41, not sure if I newer version is available to download somewhere.
I connected another unit and it shows up in NetInstall as it should so I know that part is working good. I've installed a switch between PC and router as suggested.
Any other ideas on fixing this unit?