Sorry for half info.
Do you mean that you changed the maxTests value from 5 to 100 and it still worked?
YES
I wonder if you mean that you lowered intervalMillis to 9 (not 90)?
YES and then the result is random between 89 and 91.
If I lower intervalMiliis to a lower value like 8 or 7 the random numbers are more and more varying in larger up and down values like 65 to 73 for 7 intervalMiliis value.
By "alll readings" do you mean with and without the scale.read() command?
did not changed the standard setting yet.
Did you get it to print scaleData so you could see if it is giving correct values? (I have no way to test that).
Will test this evening.
I let you know if I need more of your time 
Paco