I purchased this scope a few years ago and occasionally it has a sweep problem. The X axis will only go to about 1 block, but occasionally the scope will work flawlessly. No problems on the Y axis. I've cleaned some of the connectors inside.
Picture of it here
https://reipooom.files.wordpress.com/2011/05/oscilloscope.jpg
Picture of it here
https://reipooom.files.wordpress.com/2011/05/oscilloscope.jpg