Various reports of freezes after export over the last year or so, with recommendations to turn off showing of import dialog, turning off use of GPU, and installing a newly-released update. I've tried all of that, and am running LR CC 15.6. Windows 10 is up to date, and so are all Intel drivers.
Export and publish work correctly. The freeze in LR occurs a few seconds after the export/publish completes. Not occasional -- happens 100% of the time.
Not an issue with the plugin either, because it happens BOTH with SmugMug's publish plugin AND Jeffrey Friedl's plugin.
I don't expect that any users have the answer, but I would be grateful if someone does. This report is mainly for Adobe. (There doesn't seem to be any bug reporting system that I can locate.)
I think you found the bug report in the official Adobe feedback forum: LR CC 2015.6 crashes when using Smugmug export plug-in | Photoshop Family Customer Community. Make sure all your details are posted there. (Note that people don't distinguish between "crash" and "freeze", so that topic is the appropriate one to use.)