Ideal 5250: Problem with clamp & blade

Hi there
This is my first post: thanks in advance for the help!
I have an Ideal 5250, had it for about 3 years, been regularly serviced and blade changed every 6 months or so.
All been fine with it, until recently: it seems that when in the home position, the blade is around 0.5-1mm lower than the clamp, leaving a small (but dangerous) portion of the blade exposed.
Does anyone know the best way for me to alleviate this problem?
Thanks again
Simon