I think that you might need to grease your balls.
Sorry, cheap shot at this time of the morning. The balls in question are the counterweights on the MRH. If they don't quite get to the top (or at least one of them) then this can cause a vibration.
I could be talking out of my (****) I hope that ppruner 'tbc' comes up and benefits us all with his wisdom on the Bo 105. He has several thousand on type whereas I only have about 300.
I recall one aircraft that I flew which had a massive vibration on translation to the hover with some weird control inputs to keep it S&L. I was told it was normal but when I snagged it they found that the control rigging was 'well' out.
Good luck
btw, condolences on your few thousand on the Lynx, I survived intact with 1500!