Oh dear, oh dear.....I must be honest, I don't like replying to you with tech because you don't understand anything, you just like to dig, but, just for you, and the OP, I will explain in a little more depth, but, if you need any more help after, then forget it, it will be beyond you...🤨
In LOS the use of a waste water pressure relief is a bit sketchy, back home it was done automatically in the residence build.
When water runs down the waste pipe it pushes the air in front of it, that pressure must go somewhere, taking the smelly air with it. If the system has been well thought out, there will be no problem, but if not, or if a partial blockage of some sort, even that can cause a smell backlash.
So it depends on a few things, especially in a condo if all the residences drainage is connected, will be difficult to pinpoint.
In the OP's case, I would fit one of these, no more smells, the flap opens with the weight of water, then closes automatically by a counterweight, no water buffer, a stainless steel flap/gate...
But before that, poor a gallon of bleach down the waste pipe, it does help, might even clear a partial blockage........😉
https://www.thaiwatsadu.com/en/product/ตะแกรงกันกลิ่น-เหลี่ยม-ท่อ-2-3-นิ้ว-HAFELE-รุ่น-48561218-ขนาด-10-ซม-สีสเตนเลส-60335378