For the primary clipboard problem I opened https://sourceforge.net/p/scintilla/bugs/2287/. Surprisingly, it's the same for Scite and there was no open/closed issue for it.
JFTR: the primary cipboard problem has been fixed in https://sourceforge.net/p/scintilla/code/ci/5f9bffa5fcb0a91e68e0c3de0dd9c3d8....