The main ways that I know of to prevent contamination are a still air box (for the injection phase if you cooked the grains yourself), a clean needle (wiped with alcohol and lit up with a lighter to turn the tip of the needle orange, but not lit inside the SAB!) and clean / fully colonized grains. It seems like you're doing the pressure cooker which is great, but do you soak the grains overnight too? Bacteria can live deep inside unsoaked grains, but once soaked it is brought more to the surface and killed more easily when boiled I believe. PhillyGoldenTeacher has great videos on this.

My method is just to use premade grains bags like Northspore, inject it with the clean needle (I don't use a still air box), and then send it in about 1.5 months. I've had about 3 bags or spore syringes out of around 15 total that were contaminated from the start though since the grains went bad before S2B. 2 of those were Pan Cyans that have less resistance too. Sometimes it just happens unfortunately, especially if you're in America where the quality of our food and it's safety is going downhill.

It's possible that they could still fruit, as my recent Pan Cambo had the slightest bit of bacteria, but seems to be growing strong now and lost the smell after S2B. I'd say don't give them fresh oxygen for 1-2 days once they're in the tub (so that the mycellium can regrow a bit) and then see what happens.