T80 ALL LEDS ON ANGLED PANELS ARE LIT

Dear all, anybody familiar with this issue in the pic? all leds on the angled panel turned 100%, the issue came and went during a gig. and now it seems that its stuck with all leds 100%, anyone? hoping for a quick solution as we need the console up and running.
BEST
//
Daniel

maybe there is something really broken inside the surface…

first of all open it and make shure there are no lose parts…

Took the mixer apart, and tried all flat cables going up to the angled part, all cabling seems ok.
although on the circuitboard close to the flatcable connections, I found a battery that has what appears melted?
see pic. Anybody know what that battery does? I assume when it happened it probably damaged some other circuits

that could be the reason…

the battery buffers the memory in the surface