Immediately after updating to Opera 62.0.3331.72 (on Windows 10) this began to affect me as well. When attempting to use Ctrl-Shift-8 in gMail or gDocs to add bullets, nothing happens. I routinely use Chrome for those two pages, but even loading them in Opera itself does not work. As soon as Opera is closed, the shortcut works as expected.
Has anyone at Opera reproduced this yet?