Thanks for this information. At 3:40 we see in section that two thinwalled " half moons " transfer the differential torsion loads from left to right elevator. By deflecting the rudder different pressure exists left and right on the vertical tail, and hence the elevators see different pressure on their undersides. These differential loads travel through this drilled tube, which gives stress probably just above the fatique boundary for this metal. Conclusion : I doubt it is a ground loop problem, more a forgotten, or overseen load case. But thanks for the pictures anyhow. ( I engineered for Lange Flugzeugbau, espec. the Antares)
