determining blame of Brit-Mila mortality

The principle in Dinei Chazaka that we must be choshesh after two occurrences, is based on the prerequisite of a possible single cause for both cases, as in the case of the woman who lost two children after Mila, where there is a possible underlying genetic condition (such as hemophilia); also – in the case of the Mohel that two of the babies circumcised by him developed HSV-1, where there is the possible scenario of infection by the Mohel.
But if it was proven that the Mohel is not a carrier of the herpes simplex virus, this possibility is no longer possible, and therefore the chazaka no longer exists.
Example: when two brothers died Mechamat haMila, and a medical investigation shows that they did not die from hemophilia but from hemolytic anemia – which is a transient phenomenon. In such a case it is permissible to wait for the hemoglobin levels to rise sufficiently and then circumcise as discussed in the Gemara (Shabbat 134a) in the case of Natan haBavli