RBmAPL-2nD buggy? LAN/WLAN doesnt work

Hello, I already configured and managed several of these small WAPs, but today Im stuck with one that simply doesnt work out of the box. after first connection I could find the router both via wifi and eth connection. showed up in my winbox, but I was always disconnected after a short period of time. after a reboot, wifi is not working and eth cable is also not registering. when i disconnect the cable and connect it back, it shows up for a second in network connections, but goes down right away. once I tried this a couple of times, the LEDs (excluding wifi) were always on. doesnt matter if I power the router via adapter or POE (I also tried different adapters). now ETH cable is not registering at all, wifi is down, I cannot do anything, no way to access the device.

I was thinking if the device did not go into CAP mode, but afaik all 4 LEDs should be always on if that happened.

I tried holding the reset/wps button once again, for 5 seconds, 15 seconds.. no change.. 3 LEDs (excluding wifi) are always on. hope someone knows what the problem could be here. thanks in advance for any help.

Sounds like it is faulty. How old is it? Will the seller not allow you to return?

did you push the reset button before you power it on? then it load the backup bootloader, in case the main one is faulty

it was bought at the same time as one other that works. few days ago. however i dont know how long the seller had it in stock.
return is no problem, but when the problem can be fixed, i wanted to go that way first.

i pushed the button before powering the device on, yes. first time the reset worked. now its not responding. backup bootloader should be triggered automatically or do i need to do something here?