Steps to reproduce: 1. Press 'Ctrl+F' key combination. 2. In bottom Search bar select 'Open selection dialog' button on the right side of the bar. 3. Select dropdown arrow menu for 'RegExp' button In 'Containing text' section. Actual result dropdown menu appears for a split of a second and then suddenly disappears. It's impossible to select this menu items. Window with part of dropdown menu attached in screenshot.
Created attachment 107293 [details] select-files-window-regexp-dropdown-bug
You have to click on the "RegExp" button to activate regular expressions. Now you can select the entries just fine.