I have been using the Sundtek ATSC USB devices for many months and do not have the glitching issue you have unless the signal is being affected by weather. The ATSC market is small, so there is not a lot of users to compare information with. It is doubtful that you have a bad usb device but I guess anything is possible.
It would probably be best to contact Sundtek directly about the glitching, but the data that can be gotten from an internet website is very limited. Many developers are on Skype. A lot can be done with real-time communications set up on Skype, and a computer set up with Team Viewer. A combination like this gives a developer direct access to your equipment, and allows for tests to be made using your equipment. This is about the only way I know to look at issues with the developer and see if it can be decided as to what is causing problems. I know you do not like Skype, but it beats sending smoke signals, and it is real-time communications.