My A6 kept coming up with this error (and “Player has stopped responding. Restarting player”) so I sent it back today. I got it refurbished from the Beoplay eBay page so returning it was easy but wish it wasn’t necessary.
Have ordered a brand new one from Peter Tyson now (was £200 more but it comes with a 2 year warranty + they’re a reputable shop so fixing it should hopefully be easy if I ever have any problems).
The funny thing was the refurbished A6 was in absolutely perfect condition and looked brand new. The description said it was an open-box customer return. There was 1 existing thing in the logs from November about the DSP error so I wonder if the previous owner had the same problem and just returned it straight away too.