I know it's been awhile since you wrote this, but can you go a little more in depth about how you use the instant pot? How long do you set it for? Do you wrap the rice in a towel or line the colander or anything? Do you use it for the whole incubation or just the first step?
I just use the instant pot for cooking rice, the first 24 hours of incubation, and cooking the soybeans for miso.
koji process:
using jasmine white rice
soak rice 6+ hours
rinse rice
line collander with flimsy dish towel, add rice, cover rice with ends of towel. (I am not convinced the towel is necessary but I use it anyway)
cook rice on white rice setting ajust to low, 4 minutes
put rice in bowl and sprinkle on koji spore
mix
Put rice back in collander (no towel)
barely cover bottom of pot with water
put collander in pot
cover pot with spaltter screen and towel
set pot on yogurt setting 93 degrees F, 24 hours
check temp at 24 hours,
after this depending on temp I will put koji in another container or leave a little while longer in the pot, not turning the pot on.
when koji is done, I cook soybeans in the instant pot and use miso recipe
I find the instant pot's temp setting is pretty variable. When I started I tried 86 degrees F and found my instant pot is best at 93 degrees. I switched to a towel covered splatter screen rather than the original posts using cover with pressure button and rocker removed for aeration. Also I realized that the pressure cooker heated up on yogurt setting with out the lid. So temp setting may need to be set lower with the pressure cooking lid on. The towel on the spatter screen is to absorb moisture and maintain moisture.
I use six cups of rice and have a two level collandar with about one inch legs on the lower level. I put a little more cooked rice in the lower level than the upper level. I don't us the upper level for just cooking the rice. My instant pot is 8 qts.
The miso is delicious but I can no longer buy store bought (rather do without if it's not homemade). Same thing happened when I got chickens the eggs are so good store bought can't compete.