Here again, are you talking about BD-R DL? Those are the ones that these days are not so good in quality, if I get several coasters per 50 disc batch that's bad, to me. But some brands are approaching 1/3 coasters at times. I also had some problems with some brands of DVD-R DL but have weeded through them pretty well down to the better cost/performance ratio. I've burned about 200 BD discs in the past 2 years and prolly hundreds of DVD-r/DVD-r DL. There's lots of crap out there when you get into DL discs, and the problem is they get manufactured worse as time goes by. Some brands you won't even find in a DVD-R DL.
I'm not an authority on anything, but I've spent enough of my money to see what works for my burner and what doesn't , at least in my price range.