Heard there were bag differences ( amendment sources ) depending on region of U.S.
There has been times I had to screen the bags ( curiosity ) found a couple nails once . Most strains can tolerate it upfront and push on .
I find if I am able to recycle a bit of it after a run - it works beautifully as a seed starter mix in solos ( re-use ). No waste and that cup becomes a new plug.
It does benefit from a few “ tweaks “ tho -
More perlite / rice hull or pumice
EWC bump
Con side - Fungus gnats
This happens IMO more during transit and palletized storage . Regardless I have found a few swarmers in bags so I mix in Neem meal to 2 cu bags.
Toss it , mix it , seal it.
After that , all good.