Got my first 1 star review after 15 months and 8 courses on Udemy. No comment just the 1 star. Strange thing is student completed 100 per cent of a 5 hour course in , I beleive , 1 day. 

You think they might have decided after 15 minutes that they never liked the course ? 

My usual experience is that students who

complete 100 per cent of a course usually do so as they are enjoying it and leave good reviews ?

Don't really understand this ?