Is there a benefit to using the preheat button? Or is it just the same as going directly to the highest temperature?

Generally oven burners are at maximum (preheat) until the thermostat temperature is reached and the thermostat begins to control the gas flow.
As that isn't happening it would suggest the thermostat is either faulty or incorrectly fitted, though I must admit I am unfamiliar with ovens that either have or need a control board - I have found few domestic appliances actually benefit from the inclusion of electronics.

Generally the oven temperature will fluctuate as much as 30 degrees above or below the set temperature. The longer the oven is on, the less the temperature fluctuates. If you measure the highest and lowest temperatures readings with a thermometer after the oven has been preheated at least 20 minutes, you should come up with an average temperature somewhere within about 10 degrees of the set temperature. You can calibrate most ovens up to 35 degrees higher or lower if it is off. Any more than that requires replacing parts.

If you need further help, I’m available over the phone at https://www.6ya.com/expert/jeffrey_634abadf963e31e5

Hello,
Your oven will continue to indicate that it is preheat mode until the thermostat senses the proper set temperature. If you are getting no heat then you will need to address that issue. This could be many things but the most notorious would be the heating element. Could be the control panel as well. Some ovens have a knob for preheat, bake and clean with a separate knob to adjust the temperature. Make sure both are set properly.
Regards, Tony

Most likely the problem is your bake element. When the oven is preheating it uses both the bake and the broil element. When it's done preheating it uses only the bake element, so the broil element is heating it up, and since the bake element is not working the temperature drops until it starts preheating again.

GLOW HAS TO BE WORKING.BECAUSE ENGINE STARTED.GLOW PLUGS ARE USED ON COLD START UPS.GLOW PLUGS PREHEAT THE AIR IN COMBUSTION CHAMBER SO DIESEL FUEL WILL START TO BURN ON START UP.WHEN YOU TURN ON IGNITION SWITCH THE GLOW PLUG LIGHT WILL TURN ON FOR MINUTE UNTIL PREHEAT DONE.GLOW PLUGS WILL STAY ON UNTIL THE COOLANT TEMPERATURE GET OPERATING TEMPERATURE.THEN THEY TURN OFF.

The best way to tell if your problem is clogged jets, or bad maintenance kit, or something blocking jets. Is to look at light stripes test, and see if missing jets are all in a straight row or all over the place. If the missing jets number less that 10 you can use jet substitution to avoid the streaks. If you are using Media Sciences or some other after market ink, check that most of your problems are not in the cyan area. Media Sciences produced a bad batch of cyan which clogged the jets pretty bad. The good news is that if their ink caused the problem they will pay for some one to come out and replace your printhead. If you LST (Light stripes test) has a smear the entire vertical lenght of the page. You have either a bad maintenance kit, or a piece of paper, lable etc..rubbing against the drum while printing

Hi jepeto997:
Try these steps.
Check for and remove any media, jammed
paper, or debris found in the printers exit
path.
2. Did this correct the problem?
Complete. Go to Step 2.
2 1. Clean the maintenance kit wiper blade or
replace the maintenance kit.
2. Did this correct the problem?
Complete. Go to Step 3.
3 1. Check the exit area, exit frame, the
preheater, maintenance kit, and the
printhead (including the paper release blade)
to see if there is anything touching the drum
assembly.
2. Reseat any printer component interfering or
touching the drum assembly.
If there are streaks on the front side only of a
2-sided print, the preheater may be scraping
ink off the print.
2. Look for ink shavings along the streaks on
the printed paper.
3. Clean the preheater using the Control Panel
Remove Print Smears function.
4. Did this correct the problem?
Complete. Go to Step 5.
5 1. Possible weak or missing jet. Print the weak/
missing jet test print from the Control Panel,
see "Weak/Missing Jet" on page 5-33.
2. Did this correct the problem?
Complete. Go to Step 6.
6 1. Possible discolored jet. Print the solid fill test
print, see "Black, Red, Green, Blue, Cyan,
Magenta, and Yellow Solid Fills" on
page 5-40.
2. Did this correct the problem?
Complete. Go to Step 7.
7 1. The X-axis drive is not functioning correctly.
If the X-Axis Drive does not move the
printhead smoothly and evenly during
printing, vertical lines appear on the print.
For information about X-Axis Drive
problems, see "White Stripes (Pinstripes)"
on page 5-30.
2. Did this correct the problem?
Complete. Go to Step 8.
8 1. Smears on a duplex print can be caused by
the paper preheater operating at a
temperature that is too high or debris is in
the duplex roller or duplex paper path
guides.
2. Run the service diagnostics Duplex Path
test to check the paper preheater’s
temperature.
3. Is the operating temperature within the
correct value range?
the paper preheater operating at a
temperature that is too high or debris is in
the duplex roller or duplex paper path
guides.
2. Run the service diagnostics Duplex Path
test to check the paper preheater’s
temperature.
3. Is the operating temperature within the
correct value range?
Replace the
preheater.
Replace the
electronics
module
Hope this helps
3. Clean the paper release blade.
4. Did this correct the problem?

Technician just left our house with same issue. Jenn-Air had issued a technical bulletin as the temperature probe is mounted directly to the heating element, and measures the heat of the element, not the oven. Their fix is a revised temperature probe that goes at a 90 degree angle away from the heating element.

If your temperature is consistent, just off by a set amount of degrees, there is an adjustment you can make at the control panel.

I believe the model you have has no user-selectable temperature settings. The manual for the Magic line suggests preheating the cups as the fix. You can use the electronic cup warner OR run your tap/faucet water as hot as possible, fill the cup you're going to be dispensing espresso into with hot water while your Saeco warms up...right before you hit the button to dispense espresso, empty the hot water, dry the preheated cup and you're set! It only takes a few seconds. This way, you waste none of your coffee's thermal emergy on cup heating and your coffee will stay hot longer. Hope this helps!

Is this a gas unit? If so you might have a weak oven igniter.