NaviBot SR8855 stopped working

Hi!

My SR8855 suddenly died when it was out on a cleaning run one day.

It have had the problem that after the first start it goes back to the charging station after just a few seconds to load up fully and then it goes off and does the whole run.

I have thought it was the battery being bad and now one day it suddenly stopped and went completely black. When I manually put it in front of the charger, the charger beeps and can find the cleaner but the cleaner keeps being black.

I have taken it apart, there is around 3v coming out from the battery and I have tried to look at the on/off button, as some others have had problem with, and it is also 3v coming though that button when I put it as On.

I am not so great to understand a electrical schematic so I do not know what to else try to troubleshoot with a multimeter. I couldn't find any burning marks either.

Will add some pictures, cheers!