Why does Word constantly flash?

I use Word a lot. I tend to store my Word documents on my OneDrive for Business. For about a week or so, I've noticed that Word has a nasty habit of flashing in the background, whenever it's trying to upload the changes I've made. For example, I'll update a Word document that I've saved on my OneDrive for Business, then I'll start working on something else, so Word is in the background where it should just finish uploading the document to OneDrive for Business and stop. But that's not what it's doing. Instead, I can see in the taskbar, that Word is flashing repeatedly, as though it is trying, unsuccessfully to upload the document. It doesn't stop doing this until I intentionally go to Word - give it focus. This isn't very productive, if I have to stop something else just to get that irritating flashing in the taskbar to stop.

So, why is Word doing this?