MPX3000 and 18fps inverse telecine

Using an MPX3000 on video whose original source is 18 fps film, there is bad
jerkiness, perhaps due to its trying to inverse telecine an 18fps original as
if it were 24 fps.

Does this device have an 18fps mode (or a {fill in} fps mode?) Or is the only
inverse telecine a 24fps, and then it chokes when fed somethng out of the
ordinary?

If the inverse telecine is the problem, I suppose it could be reencoded without
the reverse; is there another solution I should try?

Jose