Since updating to the current version which is v19.10.0.1012, it happens sometimes that "Ctrl+R" starts "find" instead of "replace". Can anyone confirm this behavior?
I'm using UE v19.10.0.1012 already since release 2013-05-31 on Windows XP x86 and on Windows 7 x64. And it has happened never until now that Ctrl+R opened the Find dialog instead of the Replace dialog.
Open Advanced - Configuration - Key Mapping, click on button Show key mapping in editor, cancel the configuration dialog and check if you can see multiple assignments for Ctrl+R or something other suspect.
It could be also possible that you switch the input language by accident by pressing left Alt+Shift and not pressing any other key before leaving both keys. If multiple input languages are set in the keyboard settings of Windows, there is in the Windows task bar on right side a symbol with showing with two letters the currently active input language for the active application. I do not really expect that the input language is the problem, but nevertheless check the language abbreviation on the Windows task bar when it happens next time that the wrong dialog is opened.
I looked on this topic again and detected a possible reason why you see the Find dialog after pressing Ctrl+R.
The find dialog is opened and while this dialog is displayed, focus is set to a document window. Now Ctrl+R is pressed. This does not result in showing additionally to Find dialog the Replace dialog, or in closing the Find dialog and instead opening the Replace dialog. The behavior on Ctrl+R with Find dialog already open is that the Find dialog gets back the focus.