Ok, just upgraded to 8.0c and problems remain.
Using Sony AVC option it now says: “An error occurred while creating the media file. The reason for the error could not be determined.” It doesn’t say this in all cases, but at the resolution and bitrate I choose, it does.
Using MainConcept AVC/AAC it behaves same as before. Video is fully of blocky artifacts, and interlace flicker which refuses to go away.