Problem accessing a DC Source object with a a hardware-control from an application

Hi,
using the STM32F407 Discovery board I have an application sending data from some hardware-potentiometers to AWE objects.

Everything was working nice and smoothly, until I tried to use the combination of a 'DC Source' and a 'Param Set' object to change filter settings 
The combination is working perfectly when used in AWE Designer alone, though. BTW: I am not using the  optional input control pin for the DC Source.

This code (from Platform.c) will not find any objects:

    if (awe_ctrlGetModuleClass(&g_AWEInstance, AWE_CVcutoff_value_HANDLE, &locClassID) == OBJECT_FOUND)
            {
                cutoff_obj_found = 1;
                // Check that module assigned this object ID is "as expected"
                if (locClassID == AWE_CVcutoff_classID)
                {
                    cutoff_obj_found = 2;
                    cutoff_freq = mapfloat((float)cv_in3, 0.0, 4095.0, 10.0, 20000.0);        // in-min, in-max, out-min, out-max
                    awe_ctrlSetValue(&g_AWEInstance, AWE_CVcutoff_value_HANDLE, (void *)&cutoff_freq, 0, 1);
                }
            }

This is the equivalent data from the exported include file.

//  [DCSourceV2]
// Newly created subsystem

#define AWE_CVcutoff_classID 0xBEEF0872
#define AWE_CVcutoff_ID 30003

// float value - Data Value

// Default value: 19444.6992
// Range: 10 to 20000
#define AWE_CVcutoff_value_HANDLE 0x07533008
#define AWE_CVcutoff_value_MASK 0x00000100
#define AWE_CVcutoff_value_SIZE 0x00000001

Any idea what I may be doing wrong?
Or are there limitations to using the DC Source with external control - I did not find anything of that kind in the documentation...

Compile and link is fine, the binary can be loaded and as mentioned works perfectly when controlled by AWE designer alone.

BTW: The GUI-controls of the DC-Source will not be locked, in opposite to the Inspector of the object below. Which kind of makes sense, because the application does not access the object...

----

This is working code of the same type, where I can find no difference to the code above:

              
                if (awe_ctrlGetModuleClass(&g_AWEInstance, AWE_PeriodPulse2_period_HANDLE, &locClassID) == OBJECT_FOUND)
                {
                    // Check that module assigned this object ID is "as expected"
                    if (locClassID == AWE_PeriodPulse2_classID)
                    {
                        pulse2_period = mapfloat((float)cv_in3, 0.0, 4095.0, 5.0, 10.0);        // in-min, in-max, out-min, out-max
                        awe_ctrlSetValue(&g_AWEInstance, AWE_PeriodPulse2_period_HANDLE, (void *)&pulse2_period, 0, 1);
                    }
                }

#define AWE_PeriodPulse2_classID 0xBEEF0878
#define AWE_PeriodPulse2_ID 30002

// float period - Total period of the pulse.
// Default value: 6.0889
// Range: 5 to 10
#define AWE_PeriodPulse2_period_HANDLE 0x07532008
#define AWE_PeriodPulse2_period_MASK 0x00000100
#define AWE_PeriodPulse2_period_SIZE 0x00000001

All the best,
Mathias