My RE220 is experiencing this behavior. I unfortanately have no receipt for it from the retailer I purchased from. My mistake for assuming I wouldn't need it. Here is my description of the behavior my RE220 experiences for others that happen upon this thread. This behavior started to occur randomly and thus I don't know why it started.

The power light turns on. After a few seconds it begins to blink. After it blinks for a few more seconds, all of the status lights turn on for less than a second before they all shut off. This cycle repeats. A whining sound from the device can be heard during this process. I recall a time where the squealing would get louder throughout a cycle until the lights shut off again. The ramping up of the squealing volume repeated during the next cycles. Now when I plug the extender into an outlet, sometimes the same boot loop behavior occurs and other times nothing occurs at all (no status lights whatsoever).

Since I have no copy of a receipt and thus no way to return the device, I'd like to open it up and see if I can administer the repair myself. @David-TP Can you please ask one of the engineers you mentioned to speak about the underlying cause of the problem on this thread?

  @Underdisc Sounds exsactly the same as mine - I uploaded a video of it a few postst back - I never opened mine up.   Maybe contact TP Link, explain the situation, if its only just out of warranty to see if it will be swapped under warranty or gesture of good will.  No luck, Assuming your in the UK, Contact trading standards and open a case sometimes helps (they are great people) see of you can find bank/card statements that backup your purchse.

Do not open it as that will void any warranties and maybe cause a risk.

  @JoaoCaetano 

Same issue

  @David-TP I am not sure if I shouldn't call it a quality issue than a warranty problem. Its just been over a year and the device has conked off, which means that I cannot claim warranty. Then again, hardware is hardware after all. Poor quality hardware conks off early.