Vintage Kenmore 422 electric wall oven gets warm, not hot

Hi,

Oven details: single electric wall oven, Kenmore Series 422, may be original to house (1950s). Oven is 23 3/4 W x 25 H x 24 D. Opening is 22 W x 25 1/8 H.

Years ago, clock was buzzing and time stuck, so I pulled its white wire behind control panel to disable it. Oven has been fine until recently. Yesterday I set to Preheat at 400. It got a little warm but not hot. Set to Off, Bake, flipped breaker off and on, still not heating up. If I turn temperature all the way down, then back up, I can hear "click" when it gets past warm, so it seems thermostat knows it's not hot.

Electrical panel has twin 30-amp breakers with a bar between them, i.e. they trip or go on together, and they were on. At back of oven, 3/4" flex is hard-wired into back of control panel (no plug). Today I pulled the control panel. I get 237.9 volts across red and black Y-spades at clock. Wire insulation looks scuzzy (dirt/grime) but no burn marks.

Any thoughts on what's wrong and how to fix it? If I need to replace the oven, does anyone still make 24" wide ovens that are only 25" tall?

Thanks,
Mark
San Diego CA