Been using the 4X Windata for years in three LG burners almost without issue. One or two batches had some verification issues, and the flaws were visible - oops. Latest LG for me is a WH14NS20, but the 8 and 10 like them too. The one I just dropped into the WH14 is reported by ImgBurn to be a PHILIP-R04-000; not sure, but they are probably the same with 6X just a relabelling (since ImgBurn reports "Supported Write Speeds: 4x, 6x, 8x"). Then again, the 4X are being sold by MC for 2x as much as the 6X in 25 pack. WTF?
Take a serious look at whether a firmware upgrade might fix your burner for those disks. YL07 (05/2011) looks like the most current. I think my WH08LS20 has an older (2009) firmware than the YL07, and my two newer burners really can work with more disks; you might just need a newer burner.
EDIT: I'm wrong on a couple of counts. Windata 6x appear to be made by AVIC UMEDISC (HK) LIMITED and are UMEBDR-016-000, not the PHILIP-R04-000 made by Moser Baer India Ltd.. Also found a list of supported Media Codes for the YL07 firmware, and the UME 016 is not on the list. So, not expected to burn at all. Recognized by my WH14NS20, though. Certainly not Verbatim or Panasonic, but still better than burning Ritek, anyway... <EG>