In org-babel, when and why does `:tangle yes` prevent preceeding code blocks from being executed?

Question

I wonder if it's just me or an org-mode bug.

Often, but unfortunately not always, when I set a code block's tangle property in org-mode to yes, the tangled file gets truncated just above this code block.

In other words, the blocks preceding the block that has tangle explicitly set to yes are not tangled.

For example, in the following snippet, the block below "* Some settings" will not be tangled.

* Some settings
#+begin_src emacs-lisp
  (setq foo t)
#+end_src

* Some other settings
#+begin_src emacs-lisp :tangle yes
  (setq bar nil)
#+end_src

See also the screen-shot with the org-file in the left buffer and the corresponding elisp file in the right buffer. The first code block on the left doesn't make it into the output file on the right. This is because the second code block has a :tangle yes property. If I remove it, the first code block is included in the output.

This has given me a lot of head-ache (see also here), since my Emacs config is a bunch of org-files with elisp code blocks (one of them is partly shown in the screenshot).