Moved /usr/bin/epiphany to /usr/bin/epiphany.old and /usr/bin/epiphany-browser to /usr/bin/epiphany-browser.old, replaced originals with softlinks to /usr/bin/google-chrome, seems to work fine now; though setting the default browser in half a dozen ways and locations hadn't. Bound to be some undesirable side-effects, but hey-ho.
reverted those moves and got rid of the softlinks, in my case the issue was illuminated by this:~
turned out google-chromium.desktop only existed in /opt rather than /usr/share/applications/ , linking it in there along with all the other fixes setting default browser to google-chrome.desktop did the trick. No more getting shocked by epiphanies.