Hi Garry & welcome to Beoworld.
The service manual is available for download from the products section of the Beoworld homepage. You need minimum silver membership to access these this and other manuals though.
The chances are that aging capacitors are the problem as these are renowned for causing all manner of weird problems.
Chris.
The use of metaphors should be avoided like the plague. They're like a red rag to a bull to me.