When I first took the MBTII battery, I scored as an INFJ. However, each test I took after that scored me as a ISFJ. I have been using humanmetrics.
To be honest, I think I was a mis-typed ISFJ. Did a bit of digging and realized that I fit the ISFJ type.
And to be curious, I noticed that there is no FJ forums here. I'm rusty on my types, but I didn't think ISFJ was a rare type since I think 10% of the population was the "protector".
Makes sense considering the career path I chose XD