@Tobias – without seeing more code this is hard to answer (or to test).
Just a suggestion packed in a question: Do you make the page of the found instance the explicitly active one? Or do you rely on the mechanism, that a new selection will automatically lead to a new active page or spread?
Did you do tests with InDesign versions below CC. Maybe CS6 or CS5.5?
And if yes, are there any differences in behavior?
Uwe