'verboten' sustained N1 band,
Not only the 'OLY' but also the RB211-524 and the Trent although in this case it is the fan that has a resonance band.
The GE engines also suffer from shaft bow. Ground running a GE90 above idle requires a 20 min idle to let the shafts settle..... and they DO vibrate if shut down 'hot'!
Sorry thread drift.