I tried this on Vivaldi (same version) on macOS (13.6) and also on Ubuntu 22.04. (I don't have Fedora at hand).
I opened and closed it a dozen times, and the buttons did fail for me twice. Not only these two buttons, actually, none of the snippet links worked either.
That is a really strange issue. Quick question: does this issue only happen when you have a specific website in the background?
Thanks, I'll take a look. In general, Vivaldi is quite inconsistent with Chrome. For example, it doesn't have the Chrome omnibar code, so the tb<space> keyword trick doesn't work in Vivaldi's address bar (but works in Chrome's address bar)