Seems to me @John_Harshman is right and it wouldn’t. The balance of evidence would still be massively in favor of evolution even if the measured mutation rate deviated from expecatation by a large factor. It would just leave us with one source of evidence resulting in conflict rather than consilience. And it’s not like large variations in mutation rate are unheard of in evolutionary biology at all. Heck, in some of the lineages of the LTEE, the bacteria evolved something like a hundred-fold increased mutation rates because one of the mismatch repair pathways suffered deleterious mutation(s).
This is a stronger point, because a 50-fold increase in the human mutation rate would have massive implications for the probability of suffering both spontaneous heritable and somatic diseases, their subsequent worsening due to additional deleterious mutations, the probability and evolutionary rates of cancers, and so on. It would be extremely important to medicine.