That spike is somehow a 'bug' of the 5232K when scanning PI/PIF @4x. The disc really does not have a problem; so, it's a spike you can neglect. If you scan @ higher speeds, that spike dissapears .
I have both Nec 3500 (LD V2 B3) and Liteon combo 5232K (NK0E hacked for 12x reading; didn't like NK0H upon several tests, specially reading DVD discs: PI/PIF/transfer speeds). I have a Liteon 811s too (DVD writer) .
I use both Litey's for 'stressing' PI/PIF scanning (typical: read@4x, 811s; read@12x, 5232K). Obviously, they show different behaviour, but I have found them pretty useful for verifying burning quality, despite the fact 5232k is not a DVD writer.
I have made burns @8x (and 12x, and 4x), using the awesome nec.. and Liggy/Dea firmware.
Hope this helps ,