Not at the home PC to have a look at the tacview, but going off what you said --
1. R-27R: Well, the target is beaming.. that's enough for it to be defeated. And the target being an A-10, it was slow and probably in a notch to the radar. Hence, the missile missing.
2. For the R-73, were you against the sun? If so, it can miss. Also, was the A-10 flaring or pre-flaring?