SĒLIJA, Latvia — As NATO military staff and officials greeted the booms of successful drone intercepts with polite applause, demonstrations at the Sēlija testing range in central Latvia last week showed both the progress European startups are making in counter-unmanned aerial systems as well as the difficulty to reliably take down flying drones. After an initial intercept by local drone maker Eraser failed and the target returned unharmed, CEO Edgars Gauručs was so stressed in a later