I mean, I'm frankly not surprised. GPS is a very weak signal and prone to jamming, and the Kremlin have known to be able to do this for a long time. I don't know anything about the military version of GPS -- it is probably much more robust to spoofing, but not necessarily to interference -- but I do know that every aviator trains to navigate without GPS. It's a "cherry on the top" rather than a critically available system.