Hi funding33,
I think you are basically doing things correctly except there is an issue with Initializing the Interpreter. There is a function to Initialize the Interpreter.
Interpreter->InitializeInterp();
This reads the Var files from the *.var disk file. It also reads all the default Interpreter settings (origin index, origin offset, etc) from the *.set settings file. This initialization will basically overwrite any changes you have made to the Interpreter.
The Interpreter will automatically initialize under the following 2 conditions: #1 it has never been initialized. #2 you specify the "restart" parameter as true.
So please make the following 2 changes to your code:
#1 call Interpreter->InitializeInterp(); when your App starts and before calling your SetFixture() function.
#2 change the restart parameter in the Interpreter->Interpret() call to false.
On a side note I don't really understand what you are trying to accomplish with the ReadAndSyncCurPositions() adjustment but I assume you have a reason for this.
HTH
Regards