I purchased a Tramontina Pressure cooker, the 6 quart from QVC and I used it for months. It didn't come in with a full instruction manual. I did not know that the valve unscrewed, and I never took it out. It was made of bakelite. One day I was making potatoes, and it melted and sprayed potato all over the kitchen.
I called Tramontina and they explained how to clean the valve. Also I was releasing the pressure when the pot was hot. They suggest that you let it cool first. So, it is a bit finnicky.
I returned it to QVC and bought the 8 quart instead.
I have been taking better care of it. If I cook on LOW to LOW MEDIUM, and never release the pressure when it is hot, and remove it from the heat if I need to lower the pressure, and wash the valve every time, and wash the rubber band seal and oil the seal each time before you use it, ALL SHOULD BE WELL.
It looks beautiful. The stainless steal is well made. The bakelite and bands are the finnicky parts. I think all pressure cookers have their specific issues.