I've been noticing that every now and then my watch task would stop watching, but not give any notice that it wasn't watching. So I'd have to restart the process to get it to watch again.
I finally pinned down when this happens. So, I have by watch task running in one terminal tab and when I would run build-prod to deploy some of the changes in another terminal tab, the watch would stop as explained above.
I feel like this didn't use to happen before version 5.6.0, but I haven't verified this.