It took the best part of two hours to find the reason for the mixed mode malfunction-the lacking sweep time denominator issue. By comparison of all 84 lines going from the main front panel assy no. 08565-60002 to the analyzer, found an issue with the J1-43 line, MNL SWP (manual sweep).
Above, old version (08565-60002 A-1645-45), below new version (08565-60002 B-2430-53).
No big deal, added a yellow wire, to connect the pushbutton contact to the J1-43 line.
A quick test, and it is working just fine!
Now, the only thing remaining are the knobs, but this will have to wait a few more weeks.