Reaching out to the Brain Trust here....
I have a house on a tall crawlspace testing 5.3 pCi/L in the living area.
The kicker is that the crawlspace is encapsulated (well sealed) and has an ASD system with plenty of perf pipe, a 4" vent pipe, and a RadonAwayXP380 fan capable of moving close to 500 com max!

House is on city water and has water in drain traps. Walls are poured concrete. There is one small entry porch and an attached upper-level garage on a slab which adjoins the house for about 20': All walls and ceilings are sheetrocked, so the connection is not visible. Pre/post-mit data is not available, but typical for the neighborhood is 10-20 pCi/L. In 25 yrs I have never documented an issue locally with emanation from concrete.

I will be going over to do diagnostics with sniffer and Eco-Trackers, but would like to hear your thoughts. Thanks,