Hi Nemo1956,
I had exactly the same error a few days ago on my newly bought 8594A. It has failed on the 30kHz RWB calibration. In the service guide (HP8594A-SG) which you may get from Artekmanuals this topic is covered in chapter 5, page 49. For me it was enough to only do the crystal alignments. This is quite easy, just to be sure having some good jumpers as crystal shorts. Take care to not short the crystal test points to ground!
My 8594A has loosed it's flatness data too but this is another story....
Hope this helps and good luck!
Michael