After what you see in the video you should get
- a longer white blink followed by
- white flashing again followed by
- very brief breathing white followed by
- a longish blue followed by
- blinking blue (listening mode)
But if you can get DFU mode, try flashing your Core via USB, maybe this helps the Core to cough out whatever bothers it
Depending on your Core factory firmware, you might have to reflash the deep update in order to gain access to open and WPA/WPA2 networks (which might cause the solid magenta, if you try connecting to any of these without deep_update_2014_06).
I’m not sure, but I think to remember reading about repetitive panic attacks (red SOS codes) triggering the Core to perform a factory reset by itself, which would also wipe the deep update off, causing the need to reflash this first.
This might have been the original cause of your pain.
Just a guess