Ah, Extra Delay was not 0, I dont even know what is that slider for when it's never working when it's not at 0? Anyway all other problems remains.
Also other "Quality" settings then 100 is again different behavior, but still very same.
Ok that would explain that. Could it be that your CPU load is too high, so any small fluctuation (also in what Windows does) causes small offsets?
I've had it run all night here, with 3 different sound cards (input - FM out - normal out), FM output was at 1.0000 every time I looked, Normal M varies between 0.9986 and 1.0000. (x is still displayed as 1.0000 for 0.9986, but it is resampling a few digits further down).
For non-ASIO I/O, for a 1 second buffer, jumps in M between 0.96 and 1.04 are to be expected.