From a previous post.......

Yes, the knobs are velocity sensitive, the faster you move the knob the farther the parameter value changes. If you are trying to achieve a sonically smooth result rather than a speedy change, then you should set the resolution for the knobs for this purpose. Otherwise you are working against the "feature"... or rather, the "feature" is working against you!

If you need to move from a value of 0 to 127 rapidly you can have the knob get there quickly by turning the knob quickly: it is velocity sensitive! Yet if you increment the knob, one click at a time, it can take several complete turns to reach 127.

This reaction/response, where speed (velocity) increases the distance traversed, can make a filter sweep sound "steppy", but you'll be happy to know, it is a programmable "feature"... Simply change the resolution or curve for the Knobs.
Press [UTILITY]
Press [F1] GENERAL
Press [SF6] OTHER

Knob Curve
Adjusts the touch response sensitivity in five steps. Larger values provide higher sensitivity, letting you make large changes to the actual value even with slight turning of the Knob.
Settings: table1 – table5

Smoother changes (smaller increments) would be achieved with Table 1. Very large jumps in value would be achieved with Table 5. Using the wrong Knob Curve can cause you to conclude as you have - that the filter is "steppy" - of course, as you realize, it is not... The setting of the Knob Curve is making it "steppy" as a "feature" - it 'thinks' (at your current setting) that you are in a hurry to get to the value. When trying to get sonic sweeping results, set the Knob Curve to the appropriate resolution.

Thanks for the question. Hope that helps.