When opening a file from the side menu the editor window usually shows that chosen file. However, once there are more tabs than are visible on the screen, the editor window often opens the file and switches to the tab next to the opened file or to one of the visible tabs rather than the just-opened file.
I do have TabsExtra and Sidebar extensions installed.
TabsExtra can cause such an issue if you preview several files after each other while "fallback_focus": "last_active" is set.
Selecting a new item in the tree closes the previous previewed file before creating a new view with the content of the selected file. TabsExtra intercepts this process. When closing a file it uses an internal history to activate the previously active view. Sometimes this “activate” comes too late - means after the new selected tree item is opened. This is what you see.