For years I carried out ground runs as an engineer on various types including Bells throughout the range and non rotor engaged Alouette runs.
The criterion was that we could carry out runs on skidded aircraft without restriction. I was surprised to see that aircraft enter ground resonance as it is skid equipped however as far as I remember is equiped with dampers on the skid struts which could be the cause.
Ground running of aircraft used to be an engineers normal task, I cannot see the problem except that on entering ground resonance lifting into the hover is the first solution. I personally would be confident to do this but am sure that the way things sre now..........