FWIW I set up my 11801 using the internal trigger and feeding a ~100 kHz ramp from my 33622A. By making slight adjustments to the ramp frequency I get a straight line which intersects the graticule all the way across the screen at 5 ps/div and 2 mV/div using 5120 points and at 1 ps/div with 1024 points. The internal timebase is not as stable as the 33622A which, despite not having the high stability option, has *very* little drift relative to a GPSDO from Leo Bodnar.
I'm obviously severely aliased to get a single cycle image of a 100 kHz ramp in a 10 or 50 ps wide window. That corresponds to 10 femtosecond sampling.
If there is a time base correction that was lost I don't see how I can measure it or what effect it might have. The ramp appears dead straight though it jumps around a lot because of the 4 ps jitter of the 11801 clock. By continually fiddling with the ramp frequency I can stop the display for a single sweep with a diagonal line over the full screen from upper right to lower left when collecting 5120 points.
I'm going to puzzle over this while I fix a rather late lunch. But I can't see how there is a significant issue. I should be able to do better getting digits via the GPIB interface and supplying a trigger signal from the 33622A.
As I removed the NVRAM battery to get it to boot before I replaced the NVRAM chip, there's no question that if there were cal data in the NVRAM chip it was lost.