Problems with Read Aloud on MS Word. Is this a network issue?

I am using read aloud to help the next stage of proofreading my 11-novel series. (I got a little carried away!)

My version of word has the Natural voices version (male and female) rather than the older, more robotic voices.

But sometimes, at the end of a paragraph or page, it will suddenly pause. Sometimes this is just a few seconds, and sometimes a lot longer - 20 to 30 seconds, perhaps.

If I leave it, is usually will start up again. If I make the mistake of hitting pause and restarting it, it sometimes has lost it's place or won't stop when I tell it to.

I know Read Aloud is a server based application, so are these networking issues? It feels like it is waiting for a response from the server. That would also explain it getting confused if I hit the pause button while it is waiting - conflicting instructions.

My connection at my end is good, but I have no control over what is happening at the Microsoft end. 

Or is something else happening? And what can be done to make the experience smoother?