foxsportsgo "plug-in" failure safari and firefox - macOS 10.12.6

I'd need more technical detail in order to understand what's actually happening:

Report a Flash Player crash or error

That said, if you haven't rebooted the computer since the problem started, that's the best place to start.

If the problem persists, you might just try a different browser (e.g. Chrome, Firefox).  Chrome uses an independent variant of Flash Player.  Safari and Firefox share the same plug-in, which is also an interesting data point.  It would be really interesting to know if the problem happens in either.

In general, what I see with a lot of video sites is that they insert commercials into the video feed, but they forget to free them.  This causes the data for the entire commercial to sit in the computer's memory.  Once enough commercials have stacked up, Flash Player will run into a condition where it can't allocate enough memory for the next chunk of video, and we'll exit.  Again, it's hard to tell from a screenshot whether or not this is what's happening in Safari, but it's a pretty common pattern, even among major broadcast sites.