BLACK LEVEL BUG - is really not a flaw as much as it is a design limitation in some DVD recorders. Here in North America (and only in North America) our legacy analog video system is based on the NTSC standard. Particular to the North American NTSC standard (but not the Japanese NTSC standard) is our reference black level is 7.5 IRE (very dark gray), while every other analog TV system in the world uses 0 IRE (true video black) as the reference black level. Why? Well, in the very early days of TV, there were some technical and performance issues with the transmission and reception of TV signals with 0 IRE black levels. Of course, that was corrected decades ago and all modern TV sets and broadcast transmitters can handle 0 IRE just fine.
However, because 7.5 IRE black level NTSC is what was implemented here and in Canada, it is what we have been stuck with while the rest of the world has always been on the 0 IRE black level standard.
None of this affects digital video at all. Regardless of the format (MiniDV, Digital8, DVD, Digital cable and OTA broadcast, etc.) the black level standard is 0 IRE. This is where the "black level bug" comes into play for those of us in North America. If you want to convert North American NTSC broadcasts, VHS, 8mm, S-VHS, laserdisc (basically any analog NTSC video source) to DVD, the source black level (which is 7.5 IRE) must be "stretched" down to 0 IRE before conversion to digital. If you don't do this, your finished DVD will be encoded with a 7.5 IRE black level instead of 0 IRE. When you play back the disc on another DVD player, it will look a little washed out compared to commercial DVD's, because all DVD's are supposed to be at 0 IRE black level.
So, DVD recorders in North America should have a way to set the video input to adjust 7.5 IRE black level sources down to 0 IRE. Some do, some don't. Pioneer machines all have this feature. Newer Panasonics do (the "darker" input setting), but the older units do not. Toshiba recorders prior to the 4 series (D-R4, XS34, XS54, etc.) did not have this feature. Virtually all the cheaper Chinese units (Lite-On, etc) do not. So, people would record a VHS tape with a Toshiba DVD recorder, watch it on another DVD player, and then would see a washed out picture due to the encoded black level being off.
That's the "black level bug" in a nutshell.