I had to update firmware on 45 of these TSU500's, and when I did so I had to calibrate them by touching the top left and bottom right of the screen. 80% of the time the calibration "failed" and I had to try again, which sometimes meant repeating the process over 10 times. Most worked, but 8 out of those 45 I could either never get to calibrate, or when it finally succeeded it was off ... if I hit one button, it would activate the one to its left. I estimate it was off by about 1/4 an inch. If I tried to re-calibrate it in the setup, it would do the same... fail multiple times, work once, but still be mis-calibrated. I was hoping someone would know of a solution?