Hi There

In case my full story is too long... TLDR: Looking for ideas on how to find the cause of an earthy / musty smell in basement that comes and goes with no discernible pattern and multiple mold inspections not finding any cause.

Back in June we had a flash flood that led to water coming in through our partially finished basement window...it ran behind some old wood paneling and pooled on the (asbestos tile) floor. It was only a couple pints or so of water and was immediately cleaned up and dried, we always keep the humidity below 45% as well.

A few weeks later we went downstairs and found a strong odor... we first root caused it to the shop vac filter we had forgot to remove when cleaning the water which was covered in mold... we removed the shop vac, I removed the panels to expose the foundation wall and we called a mold inspector "just in case". Long story short we had 2 independent mold inspectors (with surface and air quality tests) both give us an "all clear" report and the odor seemed to have gone away.

A few weeks later the smell was back, this time we thought it was the Dehumidifier because after a few days of running it on high then off then high the smell seemed to track its use. We replaced it and the smell was again gone for weeks during which time I replaced the wood panels I had removed, painted, etc.

This morning, once again, the smell is back..we are confounded by the way it comes and goes (if it was mold we wouldn't think it would go away and come back...) and I am reasonably confident the area we had the water is not the problem.

There is a full bathroom and multiple sinks in the basement... if there was an odor from plumbing (traps, vents, etc.) would it be distinctly....... sewage smelling and not confused with musty?

We are in a drought here in MA with no rain in weeks - I DID ~36 hours ago replant a garden along the front of our house which abuts the foundation and gave it a very heavy watering.. otherwise the ground is dry as a bone.

Half the basement is exposed foundation so no animals in those walls or such things... there is more wood paneling I could remove on the other side but no reason to expect it would be anything but a waste of time and money.

My only other idea is to call a home inspector and see if they can look around and maybe find any areas of potential concern.

Sorry this was so long - any ideas even if far fetched would be VERY appreciated - at my wits end and have a very pregnant very anxious wife who is convinced her home is trying to kill her amid a pandemic.

Thanks in advance!