Redmi 5+ wont boot (white led blinks) with back plane, OK if open

Original problem :

My Redmi 5 plus (global version) will not turn on.

A white led is blinking when tryining to charge it.

It found a few people having found the solution to open the case and unplug the battery and then reconnect it, i confirmed it worked perfectly… but as soon as I close again the back case… it wont turn up again .

It seems like this is linked to the back panel conducting electricity of pushing a special button somewhere ?

Has anybody encountered a similar issue with a Xiaomi phone, any clue for me maybe ?