When my machine was new, Gamma ELS 7900 - and actually it is still new IMO, I used to recalibrate it about every month. It has been two years now, and I strung a little over 250 times on it (low volume), and I am finding that I have to recalibrate earlier and earlier. First, I dropped it to stringing every three weeks (no major change in volume), and now two weeks. What prompts me to recalibrate is that I am off by one point or pound in the final SBS and RT readings, and when I play with the racquet I can certain feel the softness of the string bed. Is this normal, and is there anything I can do from a maintenance wise or other steps to improve the situation? Thank you in advance.