From the Eventide TimeFactor FAQ:
"Why can't I get my Expression Pedal to work right?
your Expression Pedal has a trim pot control, try adjusting it to
either end of its range. If your Expression Pedal causes parameter
values to go from min to max and back down to min again as you move
from toe to heel, try connecting it using a stereo phone cable rather
than a mono cable."
It's funny, I solved my problems by doing the exact opposite.
@Eventide: if you have the chance of getting your hands on a Roland EV-5, try them with the TF. I bought mine used, so maybe it was modded. But if you encounter the same problems, it would be great to let your customers know of the solution as described in my other post here.
These pedals are pretty popular in Europe.