Emacs hangs while loading .org file

[David Dynerman <david@block-party.net>]

Dear list,

I have a fairly large org-file [1] (~2k lines) containing a substantial
amount of code in #+BEGIN_SRC/#+END_SRC blocks. The code is mostly
python, with one or two C blocks.

Recently emacs has started to hang when loading the file for the first
time. I saved a profiling report [2] where I loaded the file, let emacs
sit unresponsive for about 5 minutes, then typed C-g.

The report seems to indicate that fontifying python blocks is the
problem - 90% of time is spent in python-nav-end-of-statement.

Has anyone experienced something like this with large org files
containing python code? The file contains a good chunk of scratch code
which may contain python errors - is it possible that some syntactically
bad python code is causing the fontification to run amok?

If anyone has suggestions for finding the culprit, I'd be very happy to
hear.

Thank you,
David

[1] https://www.math.berkeley.edu/~dynerman/angular_xcorr.org
[2] https://www.math.berkeley.edu/~dynerman/slow-org-load