Scrub tool - Audio truncated PE 8.3.1

When I use the scrub tool and drag forwards across an audio clip I am only getting about 1 second or less of the clip playing, same goes for the entire project or selected tracks when I drag forward in the time line. Yet if I drag backwards, the entire clip will play (in reverse audio of course). This happens both on PE 8.3.1 and X1 which I am currently getting to know. I posted the problem on the the X1 forum yesterday morning but it soon disappeared without reply in the maelstrom of crazyness going on up there. Thought I would come back to the (relative) sanity down here.
 
I cant imagine that I am not using the scrub tool properly, although I will leave that possibility open. I would have thought that the scrub tool would allow playing of an entire clip of any duration if required, not just a 1 second preview, and am I totally baffled, but beginning to realise in my project just how much this function could help speed up editing, so any suggestions / comments appreciated