Over the years I've seen online multiple failures of the fiber optic, as well as had friends share that theirs, or a client's, separated.
Also I know one swat officer who had one that "just went blurry" all of a sudden. A failure I also read about online.
Another friend of mine tested about a dozen of them, over many thousands of rounds. Only 1 held zero past about 5k. The rest showed slight shifts, or loss of precision, or had unfaithful adjustments, or some other mechanical issue related to zero retention or adjustment. Also tested were several nx8, and one ATACR-1-8X24-F1. None of them had issues.
The new vortex g3 has a etched reticle, so the fiber optic is no longer a concern. Also, the internals now are different as its FFP. This said, I'll be a late adopter due to past issues I have both read about, as well as had friends personally share with me.