OK I decided to flash the mega with my usb1 port instead of the usb 3 one and the mega has recovered, interesting !
The mega is now stable and i can reach the webpage
All panels are working :
status panel : ok
power panel : all relays ok
weather panel : 3/6 sensors working
The charts are empty, maybe in the future i think.
I can stay on that version if you need some debugging information or test anything
Thank you Howard