Why Smart Cover locks the iPad when flipped at back panel after LCD re

Hello everybody,

Like many subjects on this issue i found on the forum, i encountered a weird behavior with my Smart Cover after replacing LCD ONLY on my iPad Air.

When the Smart Cover is on the screen, it locks itself normally.

But it locks itself too when flipped to the back panel of the iPad.

I read many things on tons of topics but none with clear answers to those simple question:

- what is causing this?

- where are those sleep/wakes sensors?

- how do they work?

- where are the magnets on the frame?

I precise that i only changed the LCD assembly and used the original digitizer and home button (I read some topics indicating cheap home button causing the problem)

Thanks in advance for your expertise!