While I think it is unlikely that there is a problem here, one has to consider that upgrading the sensitivity could introduce or reveal a systematic error.

Also, it is not just a correlation that has been observed - it is a correlation that has a specific form, a rising fundamental frequency that happens to in line with what we would expect from merging black holes. I know there's an element of circularity in the argument, but what are the chances of that particular sort of signal arising from a spurious correlation?