Videos are transcoded by Stream with visible compression artefacts and a big change in black levels

When uploading videos to Cloudlfare, (h.264 .mp4 30 mbit/sec 1920 X 1080p High ) through the Stream dashboard, the videos appear to be transcoded by Stream with very visible compression artefacts and a big change in black levels. I have tested many, many variables and they have all turned out the same. I have been checking the json feed directly in the Cloudflare dashboard and also an mpeg-dash player in Chrome with the same results.
Is there a way to improve the transcoding that happens when a video is uploaded to Cloudflare ? I’m sure that I am NOT seeing a lower resolution or lower bandwidth switch and I have been forcing 1080p playback every time.