It is entirely possible the slab you have does not have a vapour barrier incorporated UNDERNEATH IT. This came in the mid/late 1990's. If your house is older than that, you might have a slab that is unsealed.

All the moisture moving up through the ground and into the home is getting trapped underneath the vapour barrier. If it sits there for too long it can cause an odour.

The easiest way to check: take an extra box you have left over (1000sf of flooring = 100sf of left over product for future repairs) and open it up in your upstairs living room.

If the open box gives off an odour, then you know it is the FLOOR. And usually cork doesn't have an odour. If anything it will have a fresh cut-wood smell.

What type of vapour barrier did you use? Clear or black plastic? Or was it like white foam?

can you post a picture of your brockport oak? We are considering this color but I can't seem to find any pictures of it in a real home