Is $\mathsf{MA}$ equal to $\mathsf{NP}^\mathsf{RP}$?
In the first bullet, we would need the oracle to answer


YES, if Arthur’s check succeeds with probability $1$ (assuming the MA protocol has perfect completeness),
NO, if Arthur’s check succeeds with probability $\le 1/2$.


This sounds like a coRP algorithm, but the catch is that there is no guarantee that one of these two conditions applies for every possible input to the oracle. Thus, the oracle does not compute a coRP language, but a coRP promise problem, and the whole argument only shows that $\mathrm{MA}\subseteq\mathrm{NP}^{\mathrm{promiseRP}}$.