I have had a lot of trouble with burnt or undercooked food in my beautiful looking Kuhn Rikon pressure cooker. I had much more success in my ancient Namco cooker! I think it is because I now use an induction hotplate, rather than electric coils or gas.
Here is some information that I found that seems plausible, though I haven't yet tested it. From this link:
How to Pressure Cook on Induction
DON’T pre-heat the cooker.
I got into the habit of preheating the base of the pressure cooker on a low flame to give me time to slice onions or peel garlic cloves while the cooker was pre-heating. But, on induction, I kept getting burned olive oil and charred onions. Don’t pre-heat your cooker on induction – the cooking surface is hot and ready to saute in 15 seconds!
DO slice the aromatics first, and then turn on the induction burner just before tossing oil or aromatics to saute’.
DON’T bring the cooker to pressure on high heat.
Following the old standby advice about bringing the cooker to pressure on high heat several obvious things will happen: the cooker reaches pressure at break-neck speed (about 4 minutes), tomato sauces carbonize and bond to the base of the cooker, and the food comes out disappointingly under-done. One more thing that is not obvious will happen, too: the pressure cooker does not have time to expel all of the air and actually cooks the food at a lower temperature (mechanics explained, below).
DO bring the pressure cooker to pressure on medium heat or tack on a few minutes to the cooking time to compensate for the lower pressure cooking temperature and shorter time to pressure.
DON’T walk away from a very full or wide cooker right after you’ve adjusted the heat.
This is where the instant heat of induction does a disservice to pressure cooking. Although the cooker may have reached pressure, the sides are still at a lower temperature than the piping hot aluminum-disk-clad base. Walking away from the cooker once the heat is lowered will cause internal pressure to quickly fall since the heat generated from the base is not enough to both keep the food inside boiling and maintaining pressure and heat up the rest of the cooker or food.
DO hang around to make heat adjustments for the first 5 minutes of pressure for very full or very wide cookers.
DO use the induction burner’s timer feature to set the pressure cooking time so the burner turns itself off automatically when time is up!