'frame' object is not callable

I am receiving the following traceback on occasion. It appears to be a non-deterministic failure. Once it does happen, it continues to happen (on all served pages) until I restart my Plone cluster. Has anyone seen this, know what's causing it, or how to prevent it?

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Here is the full error message:

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Traceback (innermost last):

Module ZPublisher.Publish, line 138, in publish
Module ZPublisher.mapply, line 77, in mapply
Module ZPublisher.Publish, line 48, in call_object
Module Products.Five.browser.metaconfigure, line 485, in __call__
Module Products.Five.browser.pagetemplatefile, line 125, in __call__
Module Products.Five.browser.pagetemplatefile, line 59, in __call__
Module zope.pagetemplate.pagetemplate, line 132, in pt_render
Module five.pt.engine, line 98, in __call__
Module z3c.pt.pagetemplate, line 163, in render
Module chameleon.zpt.template, line 261, in render
Module chameleon.template, line 191, in render
Module chameleon.template, line 171, in render
Module 095c12335ba77b9536d2ed24843a4f5d.py, line 246, in render
Module d6d4afbc0e11c2016e75a3e8749617bd.py, line 1223, in render_master
Module d6d4afbc0e11c2016e75a3e8749617bd.py, line 438, in render_content
Module z3c.pt.expressions, line 71, in render_content_provider
Module zope.viewlet.manager, line 112, in update
Module zope.viewlet.manager, line 118, in _updateViewlets
Module plone.app.layout.viewlets.content, line 58, in update
Module plone.memoize.view, line 47, in memogetter
Module plone.app.layout.globals.context, line 238, in actions
Module Products.CMFPlone.ActionsTool, line 82, in listActionInfos
Module Products.CMFCore.ActionInformation, line 206, in __getitem__
Module Products.CMFCore.Expression, line 47, in __call__
Module zope.tales.expressions, line 217, in __call__
Module Products.PageTemplates.Expressions, line 155, in _eval
Module Products.PageTemplates.Expressions, line 105, in render
Module Products.PageTemplates.ZRPythonExpr, line 66, in call_with_ns
TypeError: 'frame' object is not callable

 - Expression: "provider:plone.belowcontentbody"
 - Filename:   ... egg/Products/CMFPlone/browser/templates/main_template.pt
 - Location:   (line 108: col 74)
 - Source:     ... 
 - Arguments:  repeat: {...} (0)
               template: <ViewPageTemplateFile - at 0x7f5e606bbb10>
               views: <ViewMapper - at 0x7f5e59c20dd0>
               modules: <instance - at 0x7f5e71e3b2d8>
               args: <tuple - at 0x7f5e79161050>
               here: <ImplicitAcquisitionWrapper about at 0x7f5e60d5b820>
               user: <ImplicitAcquisitionWrapper - at 0x7f5e60b70a50>
               nothing: <NoneType - at 0x8fb4d0>
               container: <ImplicitAcquisitionWrapper about at 0x7f5e60d5b820>
               request: <instance - at 0x7f5e5a3a9518>
               wrapped_repeat: <SafeMapping - at 0x7f5e5a3ed9f0>
               traverse_subpath: <list - at 0x7f5e5b83e050>
               default: <object - at 0x7f5e7907d540>
               loop: {...} (0)
               context: <ImplicitAcquisitionWrapper about at 0x7f5e60d5b820>
               view: <SimpleViewClass from /data/plone/buildout-cache/eggs/plone.app.contenttypes-1.2.17-py2.7.egg/plone/app/contenttypes/browser/templates/document.pt document_view at 0x7f5e59c20c50>
               translate: <function translate at 0x7f5e5a463410>
               root: <ImplicitAcquisitionWrapper Zope at 0x7f5e5b889fa0>
               options: {...} (0)
               target_language: <NoneType - at 0x8fb4d0>

If I were a betting man, I would wager that this was another symptom of my Python binary that was segfaulting. I will keep an eye out for it again, but I (want to) believe this was merely a red herring. The details can be found here: