This is a different issue from #454. This is not a Python exception, but a crash in CPython. It is hard to reproduce. Earlier I've reproduced it multiple times when loading Google website, but now I can't. I'm also trying with https://cnn.com/ (which has a lot of frames and content), but also no luck at the moment.

During the crash the last log messages were (CefShutdown not called):

[0817/175818.046:INFO:cef_log.cpp(8)] [Browser process] V8ContextHandler_OnContextCreated()

[0817/175818.124:INFO:cef_log.cpp(8)] [Browser process] LifespanHandler_OnBeforeClose

[0817/175818.124:INFO:cef_log.cpp(8)] [Browser process] del g_pyFrames[1#2]

[0817/175818.125:INFO:cef_log.cpp(8)] [Browser process] del g_pyBrowsers[1]

[0817/175818.128:INFO:cef_log.cpp(8)] [Browser process] GetResourceHandler: Browser was already globally unref
erenced, a new incomplete instance is created, browser id=1

When debugging issues with cookies not flushed to disk (#365), I noticed that after browser is closed there are still a few callbacks being executed from CefRequestHandler: GetResourceHandler, GetCookieManager and OnBeforeResourceLoad. I have an idea to check if browser is already closed and in such case do not execute any code in these callbacks. Check with such code:

        if browserId in g_unreferenced_browsers \
            or browserId in g_closed_browsers: