Hi,
I see your log A14AC18C here..
Your description is "Choose “eject CD” from context menu",
but it the log I see that the MediaMonkey got WM_CLOSE message and was actually closing (and there was an exception when trying to pretty-print persistent.json file), still analyzing why this could happen..
Are you sure that you haven't initated closing of the MM5 window (either by mouse or by keyboard) and you just selected the 'Eject CD' action?
EDIT: Could you please open
Support Ticket for this issue, I would send you special build that would log the JSON to find what's wrong here..