I've got the EBY701 myself, and haven't had any problems. I did have some issues with my previous screen that ended up being a bad controller - never bothered to fix it.
However, in the process I got some good troubleshooting steps - first, are you using the latest drivers? I used the following:
http://210.64.17.162/web20/eg/drivers.htm
The best step I (if it's a hardware problem) thought was to test with the case completely open and nothing touching the touchpanel (remove the front fascia so it can't press on the edges of the panel). See if it still loses calibration. If it does, you can try a new panel, or a new controller, or both. I think someone in the classifieds was selling controllers - he might still have some.
Otherwise, you can try to RMA the thing because it does sound like a hardware problem.
Good luck!