You're not feeling the "bouncing rotorshaft" nor the play in the bearings. That play is normal and required to be there for component to operate correctly. As stated in the Bell explanation the vibration you feel comes from the M/R blade track which is set to the minimum blade angle after maintenance. A minimum blade angle setting is required any time the M/R assembly or M/R control rigging as been changed to include BO105s. The purpose of the minimum angle is to ensure on the 1st flight check after that maintenance in the event of an engine failure there will be sufficient M/R RPM to perform an autorotation. Once the final flight M/R work is complete and the auto RPM set, the minimum blade angle has usually been adjusted out.

However, in some situations the minimum blade does not get adjusted out or it is very close to the extremes for the stated auto RPM settings. This is also mentioned in the Bell explanation. So the maintenance solution to fix this bounce on the ground is to readjust the autorotation RPM which works most of the time. Or, you can continue to pull in a little collective everytime. However, in some scenarios pulling in a bit of pitch can create other issues.

Well just my opinion but
1) Check that outo RPM is correct for the ambiant conditions. Particularily if you have changed operations from hot to cold. Adjust as required.
2) zero the trim tabs.
3) empty the blade bolts of any weights. ( we one found weights in both blade bolts)
4) Do a complete track and balance. This is also a good opportunity to fine tune idle settings, gen matching and all the other small stuff you have been meaning to do.
5) If that solves the problem do another check of auto RPM and return to service.
6) problem is not solved check all the weird stuff.
I think that a T+B should be done every 100 hrs. A smooth aircraft has fewer snags.