You’re probably using Chrome, Edge or Opera to paste into Google Docs or your CMS. Try it in Firefox. Behavior reported at link below, and it hasn’t landed a repair ticket. 
RC4 - Scrivener HTML clipboard not recognized in Chromium-based browsers. Plain text only.
(Stipulations: Thread should probably be moved to the Beta forum. I consider this a bug very much in need of repair. OP and I are unknown to one another.)
Cheers - Jerome