Hello Jim

This is not an uncommon problem and is likely to need the
microprocessor replacing with an upgraded part (not a DIY job) to
ensure long term reliability, and possibly other components.
Your first port of call is your supplier but it is likely they won't
want to know.
If you have documented service history I would suggest contacting Sony
directly they may be able to help.

It does not have a backup battery as such the corruption is caused by
mains spikes.