e-perm testing reliability

I have just had a radon test which came up positive. About 5 years ago, I tested and had the following results: Basement 1.3, 1.5; First Floor 0.8. Now I'm being told that my 48-hour test is reading 9.4, 9.4 in basement and 5.4 on the first floor. I'm having trouble believing the results. I am not aware of one other home in our 600+ home development with radon problems. Not one. Nothing has significantly changed in the foundation, etc. What is the probability that the tester fouled up? And what are the ways that an e-perm can be fouled up. Thanks.