Electric Oven Troubles

This is a long shot but I'll put it out there anyway.

I have a vintage 1970 Gaffers & Sattler electric range with "Automatic Cooking" on the oven. The manual is long gone. The oven works fine -- when it works.

There are three knobs on the front panel together with a time-of-day clock. There is also a 60-minute timer associated with one of the knobs. Another knob sets the time of day. Some of the knobs are push-pull, that is, they lock in a "push" or "pull" position.

Sometimes the oven heats up and sometimes it doesn't. When it doesn't, I have to fuss with these knobs and get them in just the right configuration for the oven to heat up. When the oven doesn't heat up, it is not clear how the knobs got out of kilter and out of their previously-working configuration. It isn't clear from studying them how to configure these knobs so that the oven comes on at all times when the thermostat is set.

If anyone can illuminate the function of these knobs I would greatly appreciate it.

Thank you.