A slightly longer TRGB output shaft usually fixes the problem of contacting the tailboom. Isn't that how they cured the AS350 problem in the early days?
Might mean a complete re-design of the gearbox, aahhh, what the heck lets just try the cheaper band-aid fix instead!
Still some un-answered questions in this incident though, like how can the T/R contact the boom without closing the gaps (as DNR) has written?
Is there an assembly issue? ie was the spacer on the output shaft in its correct place?