The oval burner has only very low flame, even when set on high

It might be from the burners being dirty or from the electrode not being properly sealed.Or the burner head and the caps are not correctly have been matched up.

Use a manometer to insure lp gas pressure is correct. The regulator for the stove may need adjusting. The air mixture adjustment may not be correct for PL as well.

Hi,

The simmer adjustment is behind the knob for each burner.

Here are the instructions from the installation guide. Let me know if you have questions.

either turn down the gas knob or turn knobs to lowest setting without going out. That is about your only options

Remove knob, with flashlight look down top of shaft see a slotted screw that screw is flame adjustment.

To adjust, light burner, turn flame to low, with screwdriver turn screw rite till flame is at desired hight (aprox 2mm). now turn up to high check that high is satisfactory if high is to low then adjust screw. check low again. adjust till both setings are acceptible.
do for all burners

Remove knob, with flashlight look down top of shaft see a slotted screw that screw is flame adjustment.

To adjust, light burner, turn flame to low, with screwdriver turn screw rite till flame is at desired hight (aprox 2mm). now turn up to high check that high is satisfactory if high is to low then adjust screw. check low again. adjust till both setings are acceptible.
do for all burners

As for holding the knobs that is common with this stove, you could check to see if flame is hitting sensor the burner hole that lines up the sensor may be dirty.

Get the installation manual for your range, and find the part on adjusting the low heat for the burners. On my Whirlpool, I found there is an adjustment screw inside the control knob shaft of each burner. The manual says turn the burner on low, remove the knob, then turn this screw until the flames are 1/4" high. Super-easy, it took me 5 minutes to do. I am sure all ranges have similar adjustments, might be in different locations - check the manual.

I am hesitant about answering your question because if the flame is adjusted incorrectly it could be dangerous.
Remove the knob and look inside the stem of the gas valve. You will see a very small adjustment screw. This is where you adjust the flame for the burner.
What I usually do is light the burner and turn it to the lowest setting. Hold the stem in this position and turn the screw. They are usuall kind of stiff to turn.
You want to adjust the flame so that it just comes to the top of the burner cap at the low setting.
This is the important part!!!
When you have got the flame adjusted, put the knob on and turn the flame to high. Quickly turn it from high to low, if the flame goes out, adjust it higher. Repeat this test until you can turn it from high to low quickly and it stay lit.
Also important to remember. When turning the screw, a little turn goes a long way.
Post back if you have any questions.

there are two considerations for burner height. 1) the gas adjustment screw on the knob and 2) the gas-air mixture to the burner. establish a flame and adjust the screw for a standing flame at the burner. adjust the gas-air ratio orifice so that the flame has no yellow tips.

it appears that the air intake intake is incorrectly set or you have the incorrect gas jets fitted to the product. Regards Engineer