Despite promising results, clinical translation of myocardial arterial spin labelling (myoASL) is hampered by insufficient reproducibility and robustness. We investigated the influence of physiological and sequence parameters on FAIR-myoASL in simulations as well as phantom experiments, and developed a correction method based on separately acquired T1 maps. Our simulation and phantom results show acquisition related MBF differences, potentially undermining the reproducibility of myoASL measurements. Inaccuracies between true and reconstruction blood T1, further render the sequence susceptible to heart rate variations, particularly for larger T1 mismatch. Using accurate blood T1 times in reconstruction may improve robustness and reproducibility.