How do you defeat a swarm attack scenario that uses INS with other existing onboard sensors; EW countermeasures in the RF spectrum would be useless. Optical terrain maps exist that could algorythmically work with INS to verify position in conjunction with barometric altmiters.
Over the short distances drones fly INS will be more than near enough. However, for small amounts of explosives you have to be REALLY close, that requires some sort of manual spotting and flying.
Of course, a clever first wave would be one that homes in on any transmitters to take out a jamming device. Similar tactic to ALARM/HARM used by the military for radar.
I cant see anything on the video that rules out an uplink jamming. It would only work over a short area and cause the behaviour we saw.