Have you tried turning off "Audio & Video File Scanning" under "System / System Services / Web Content Filter"? This fixed the problem for me. I found it earlier but forgot to mention. Now Netflix is nice and smooth.
Props to RFCat_vk for reminding me.
https://www.astaro.org/beta-versions/project-copernicus-public-beta/58831-information-there-bypass-streaming-media.html