It seems slider of Pre 3 cut the volume flex cable (ribbon) to half. It is the same cable which is connected to 3,5m headphones plug.
I have noticed in the forum that many users had same problem and that this is old issue from Pre 2 too.
Flex cable is glued to the main board by conductive golden tape and this one gets loose after certain time and slider catches it and slice the ribbon.
Does anybody knows where to get one or if someone have a new spare or one from broken Pre 3.
Part number is 171-10574-00 Rev A followed by this markings HMSF 2311 5052A