Came across this bug for the first time today: if I highlighted words directly beneath another highlighted section, the original highlighted phrase would "break apart" into separate highlighted words. I was able to go back and get everything highlighted properly but once I hit submit one of the phrases broke apart again on its own. So I'm unsure if the program counted it that way or if it was just displaying it to me as unconnected.
This only happened with phrases containing words with a hyphen (ex. "... and aggregation of alpha-syn is ...") so I suspect that's where the issue is coming from. I've only seen this happen in one doc so far but I'll reply here if I encounter it again.