Try make two different parts where both parts only contain the movements of one slider (respart and cutpart).
If you open these parts as "list edit", every entry should be like:

time, controler name, control number and value.

The control numbers in the tow parts should be different. The reason its called "Unknown controller" is that its not all controller numbers that are defined for all instruments.
You know like the sustain pedal which is CC64.

If you still cannot make it work mail me, attach the .arr file with the two parts