Hi, and sorry,
I have written some nonsense, as I did not fully read the error description..
All of these failing tests you've reported, all check the Ohm compliance voltage, not the Ohm current sources themselves...
That means, it is checked, that in case of overload in Ohm mode (open or too high resistance per Ohm range), the output voltage does not not exceed 7V(+-3.5V).
I expect, that this compliance voltage is too high..
You may check that, by choosing a fixed (manual) 2W Ohm range, e.g. 10k range, and measure the output voltage between Hi and Lo by a multimeter (10M or infinite input resistance).
I bet it even exceeds 10.5V, where it should be limited to 7V typical.
There will be a failure either in the +18V power supply (which would endanger your whole instrument), or zener CR203 is short, and applies more than about 13V at pin 3 of Fineline resistor array U102D. See schematics page 9-10 or pdf page 157.
Zener failure is most probable, I think.
This CR203 has 4.7V or 5.1V, depending on vintage of your instrument. Therefore check with shorted Ohm input, if it zeners about 4.7..5.1V.
Your description indicates, that every other component in the Ohm current source circuitry is ok.
Frank
PS: On my old HP34401A, I just checked the output voltage in overload condition, with an 10MOhm voltmeter:
It ranges from 7.8V in the 2W-100 Ohm range, up to 8.4V in the 2W-1 M range.