Please let me remind you about coherent sampling. Try to achieve this for all your test signals. My tip of today is to write a matlab function for it so that you can easily create your vector with a sinusoid. Also do not forget to always create a vector that is equal to 2 to the power of some integer number, e.g. 1024, 2048, etc.
See the function
daisyPrimeSig.m in the daisy/m directory, which create coherent sampling frequencies with a prime number of cycles.
Notice also that for too short vectors there might even be cases where coherent sampling with a prime number of cycles/periods can be met.