Alright, I got it to work by changing the following settings (before > after):
Resize Tab:
Maintain Proportion: None (Distort) > Letterbox (Pad)
Preprocessing: Nothing > Lowpass for large Downscales
Interlace: Automatic > Progressive
Input Display Aspect Ratio: Derive from Source > Assume Square
Output Pixel Display Ratio: Automatic > Square
Output Pixel Aspect Ratio: Automatic > Square
H264 Tab:
Encoding Speed/Quality: 100 > 90
Display Aspect Ratio: From Source > 1:1 (Square)
Initial Buffer Fullness: 100 > 90
Number of Slices: 1 > Automatic
Would anybody have a hunch or know even which one of these settings might be responsible for the errors encountered before changing them?
Cheers,
Y
Yann Heckmann - Editor & Color Grader - London