The voltage you are reading comes directly from the oven thermostat (NLA) thru the door lock switch to the ignitor and gas valve. A technician would start at the thermostat to verify that there was 120 volts at the Bake terminal to neutral when Bake is selected. If there is, we know the problem lies between here and the ignitor, usually at the door switch. Only thing, you said the broil works fine, so the door switch may not be involved. Grab your meter and check the oven themostat.
There's also an outside chance that the coils in the gas valve on the bake side are messed up, causing a drop in voltage to the ignitor. Meter checks tell all.
0307378 is the part number on your oven thermostat, sadly it is not available any longer.