Strange behavior flex charging cable

Hi, i have the following issue with the charging flex board.

Hoping to be clear

1) I have 2 G2, one is working (A) and the other one isn't working (B)

On B the red led is blinking if I plug th phone to the supply charger

2) I swap 2 flexes board

Result: now both G2s are working

Basically A with the flex originally in B (that wasn0t working) now is working

And B is working with the flex originally in A (that already was warking)

3) I partially disonnect the flex ffrom the A (remind, it is working with B flex that at the beginning wasn't working), I place correctly various sensors, I connect again the flex: now it isn't working

If I switch 2 flexes, I have the same behaviour of point 1

It is quite clearly the 2 G2s are working but it seems the flex that originally was in B has some issue... what I'm not able to explain myself is the reason why at the beninnig, the first time I switched 2 flexes, both were working but after partially disconnect and then connect again it wasn't working again.

Someone had some similar experience/suggestions?

Thanks