I had this same problem with a 575A model. Although cleaning the lens helped for a while the only solution was to replace the laser lens assembly because the laser gets weak after a few years. They cost about $25 from ebay and it really is very easy to change the module over.
Pioneer Parts still sells the laser head also. It was $78 the last time I checked. My 563A has the problem reading the SACD layer but only on certain discs. If it gets worse, l plan on trying a laser replacement. Pioneer Parts lists the same laser head for the 563 and the 578.
PMFJI - I just want to mention that I scored a Denon DVD-1940CI for $50 + $20 shipping for a friend. I scored his cousin (my guitar tech) one of these units brand new for $88.88 in 2009 and it has never failed.
I used to have one of these Pioneer DV-578A players and finally got tired of the issues it had.