Scrivener has worked poorly for me when copypasting to any program, due I think to something in Chrome itself working with the app. I have this problem on any website I use.
What I've learned to do to prevent this is these steps:
-Copy from Scrivener
-Ctrl+Shift+V paste into Open Office (presumably any word processor works the same), which keeps the formatting
-Then Ctrl+V paste as normal into the website.
It's an extra 20-30 seconds that annoys me a little bit but it always works for me at least.
EDIT: You already figured it out lol. Sadly it'll take Scrivener to fix this, I think, not Tapas.