Folks!! If you have one of these SSD's and are seeing write speeds dive into the basement, don't put the blame on your A/V vendor nor your OS manufacturer. Its 100% an Western Digital issue. Its no less than, the second time for WD concerning throttling this year.
https://www.neowin.net/news/new-wd-sn550-ssds-allegedly-crippled-to-half-write-speeds-when-out-of-slc-cache/