Earlier quoted context omitted.
There's been a long-standing issue in Rider and also Webstorm where you try to search globally with Ctrl-Shift-F, and the search UI comes up with the searchbar unfocused and pre-filled with something random. You type what you avtually want to search for, and it either goes nowhere, or tacks onto the end of whatever garbage was pre-populated in the search bar.
This sounds like this one: https://youtrack.jetbrains.com/issue/IDEA-201301 It's a third-party issue that we, unfortunately, can't properly address on our side but there's a workaround available.
If some text is highlighted, the Ctrl-Shift-F dialog will populate with that text, and it will be focused and selected.
If nothing is highlighted in the editor, then it uses some random bit of text from the search history buffer, and does not focus the input.