If the smell is indeed biological, try running a few cups of Lysol laundry disinfectant. After that, add 1/2oz to the fabric softener for each load for a few weeks to maintain and continue to create an environment where that stuff can’t grow back.

I second this. The first time I fully removed my detergent drawer I almost vomitted. I ended up putting vinegar in a gallon pump sprayer to get way back in there. Now I remove the tray once per week to let it dry out.