Having just posted about DCFLDD, my good friend Jim also pointed out that I had ignored the issues with FAU-dd from George Garner. Helix uses this dd version on the Windows side, specifically because it supports the \\.\PhysicalMemory device to grab RAM. It has been noted that even if the block size is set to 512b FAU-dd still copies data at 4096b to increase speed. however, if it encounters a bad block it will skip 4096b.
The latest version from George steps back from 4096b to 512b when a bad block is found to minimize lost data but unfortunately support for \\.\PhysicalMemory was removed in that version. This is only an issue if bad blocks are found. Removing the noerror switch will stop dd if errors are found and enable you to use a different tool if you are concerned about this. (do not remove the noerror switch when imaging RAM, it will stop almost immediately)
Also, to get around this, FTK imager is installed on the Windows side and there are no reported problems of this type with that tool. However, running from a GUI will have a greater footprint on a live system.