This Dyson V8 has no power, battery led indicators are working fine, the battery is charging, and replacing the battery didn`t solve this issue.
It looks like one of the battery lead connectors is loose and creates a bad connection with the mainboard.

I suspect that the screw entered the terminal on the board crookedly and the torque limit set on the screwdriver was reached, so the technician moved on to the next screw, without noticing that the screw is not mounted correctly.
Due to the high current, the terminal on the wire was welded to the terminal on the board and it worked like that for a while until, due to vibrations, the wire came off and could not be welded back due to the accumulated oxide on the terminals.