@Renard

Hi，Thanks for the feedback.

I see your original post here:https://community.tp-link.com/en/home/forum/topic/581130

Like Heidi_Alp said there, this open WiFi will only show up after Deco is reset and is only used for set up and flashing blue light also means Deco is in set-up mode.

So currently, the issue is more like Deco E4 randomly reset itself.

How about the second question that Heidi asked and did this unit respond to reset, like the LED will change to flashing yellow-solid yellow-flashing blue?

While if it did turn to flashing yellow-solid yellow, back to flashing blue, which is expected and you could refer to this link and try to add this unit back:

https://www.tp-link.com/en/support/faq/1590/

If it kept flashing blue even during the reset, I am afraid that you might have a broken unit.

Thank you very much.

Best regards.