@shari the problem is intermittent and symptoms are not always the same. But the root cause is surely that the SACD laser is failing.
I contacted Music Technology (thank you @czbbcl) and they're not interested in tackling the problem. They say the original laser is no longer available and the aftermarket ones are unreliable. I did buy one from ebay and my local shop was unable to make it work - he put it back the way it was, so I'm now left with a very good CD player.