Say I have one file open. I see a tab with its name above. Now, when I single-click on another file in the folder list, its contents are immediately displayed in the editor, but there is no tab with new file name shown. So, content of the newly clicked file are displayed under the tab of the old file (tab is actually shown as inactive, but it's still the only tab there). Similarly, if no files were open, there will be no file tabs at all.
If I double-click file instead, tab is drawn. If I single-click and start editing, file tab is drawn as soon as there are file changes.
This happens on both Linux and Windows. I tried latest build 2169, bug is still here.
Off this topic - is it possible to move minimap to the left of file content?