Struggling to download. Goes to blank screen for trailers.

[Sam361]

When downloading a trailer for a film it just goes to a blank screen. 

It will only download one program at a time and takes ages. Can only watch the program next day. Anything else is queued.  We have to download anything the day before. 

[Mark39]

By design you can only download one thing at a time. The slow download speed is probably because of poor WiFi where your Sky box is positioned.