One more observation is that, in the older database ( in 6.1) the type of label for "dsp('sheetIndex)" on the symbol is "sheet label". In 5.1.41, there is no such option. The type of label for the 5.1.41 data is currently "instance label". Now it makes me think if this is an added functionality of OA.
I am not sure where to look for the custom code as well if there is one.
Not sure why you started a new thread for this. Anyway, the key factor will be that the label is an "ILLabel" (which means it is interpreted as a SKILL function call). Unless the dsp() SKILL function is defined, it's not going to work...