XINDAK XA6950 schematic

Hi all
after many years of work, my 6950 starts to show some issues when turned on.
The volume control starts showing random values rather than the one that was left before being switched off the day before.
Moving back the volume there is a "error -2" message (indicating a mismatch beteween the volume and the value indicated on the display).
Switching off-on again everything goes fine.
When the working temperature is around 40° (display indication) everything goes fine.
As I hear a relè with a bad noise during the seconds before the "error -2" message, l suspect that maybe the reason.
Does anyone have a schematic to help?
My version is the full solid state 6950, not the hybrid.
Thanks in advance for your help.