Double free or Corruption error when using GeoDjango

I am running django 1.9.4 on gunicorn19.4.5 with the gevent worker (gevent==1.0.2, greenlet==0.4.9). My app is deployed on heroku. For some requests, I have noticed this error: "*** Error in `/app/.heroku/python/bin/python': double free or corruption (out): 0x000000000403bc90 ***". I can't reproduce it deterministically, but it happen in about 5% of all requests. I was able to get the stack trace for it and everytime it's the same:

May 19 13:50:35 <app-name> app/web.2:    File "/app/.heroku/python/lib/python2.7/site-packages/django/contrib/gis/geos/geometry.py", line 125, in __del__.

May 19 13:50:35 <app-name> app/web.2:      capi.destroy_geom(self._ptr).

May 19 13:50:35 <app-name> app/web.2:    File "/app/.heroku/python/lib/python2.7/site-packages/django/contrib/gis/geos/libgeos.py", line 157, in __call__.

May 19 13:50:35 <app-name> app/web.2:      return self.func(*args, **kwargs).

May 19 13:50:35 <app-name> app/web.2:    File "/app/.heroku/python/lib/python2.7/site-packages/django/contrib/gis/geos/prototypes/threadsafe.py", line 52, in __call__.

May 19 13:50:35 <app-name> app/web.2:      if not self.thread_context.handle:.

May 19 13:50:35 <app-name> app/web.2:    File "/app/.heroku/python/lib/python2.7/site-packages/gevent/local.py", line 173, in __getattribute__.

May 19 13:50:35 <app-name> app/web.2:      d = object.__getattribute__(self, '_local__dicts').get(getcurrent()).

May 19 13:50:35 <app-name> app/web.2:  *** Error in `/app/.heroku/python/bin/python': double free or corruption (out): 0x0000000003dd6470 ***

Can someone tell me what's going on? How can I fix this?

Thanks for any and all help,

Tapan

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