Maybe it's been mentioned in the mass of DCT posts but when you get a bad shudder/vibration/chatter when letting out the clutch on any manual transmission it is usually attributable to oil on the friction plate. The operative term is "friction" and the oil on the absorbent friction plates makes friction application inconsistent. The Focus DCT is a manual transmission (kind of like two manuals bolted together each with its own clutch) one clutch works 1, 3, & 5 and the other 2,4, and 6. It is possible for one to experience a shudder only in 1, 3, & 5 if only one clutch is contaminated but this is unlikely since the primary cause of contamination in a new car is internal oil seal failure.
If you drive a normal manual with a foot operated clutch, you can also generate a very mild shudder by slowly letting off on clutch peddle (engaging the friction plate with the flywheel) while not applying increased fuel feed and this condition can also be felt with the Focus DCT when creeping forward/rearward slowly (although it tends to be lessened with time as the friction plate/flywheel interface wears in).
2012 Focus SEL 303A, moon roof, etc
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1975 Jeep CJ -built
1974 Dodge W300 Power Wagon dump truck
2002 Kubota B-21 tractor-loader-backhoe