I`ve not flown an EC135,so my comments relate to approx. 30 other types that I have flown and tested.All have limitations for certification,military and civil,being either Vne,enginepower/rotor Tq, weight,CofG,SIDEWAYS flight,BACKWARDS,and RATE of YAW. They are usually determined when the amount of control used is within 5-10% of full control authority as determined/set by the manufacturers,to allow a little margin for error. If you use ,as has been said,full yaw,whilst hovering,possibly outside the sideways/x-wind limit,and the a/c about-faces,that is your problem,and you may not have 700ft to play,or pray with!
Not only that,operating consistently outside the limits will put up the amount of power reqd,by the t/r drive shaft ,and gearbox; it may well fail,maybe it will fail with someone else,who may well be flying within limits one day.