Problem seems to be that the input uses a custom color matrix and Hybrid guesses Rec.709
from MediaInfo:
The preview needs to convert to RGB uses Rec709.
-> Since you are not doing any YUV<>RGB during conversions the encoding probably doesn't look right since the colormatrix signaling is also bt709.
So signaling another colorMatrix (or none) might fix the issue during playback. Preview can't be accurate with custom colorMatrix.
from MediaInfo:
Codec settings : CustomMatrix
Codec settings, Matrix : Custom-> Since you are not doing any YUV<>RGB during conversions the encoding probably doesn't look right since the colormatrix signaling is also bt709.
So signaling another colorMatrix (or none) might fix the issue during playback. Preview can't be accurate with custom colorMatrix.