So there are three numbers: the expected expansion based on Planck measurements of a historical value based on cosmic microwave background, red shift of distant supernovas calibrated to nearby Cepheids, and an independent value obtained from LIGO based purely on gravitational waves, which still has uncertainty that encompasses both of the others, but will sharpen in coming years.

The LIGO measurement is not subject to vagaries of electromagnetic effects that could be introducing anomalous redshift, or to possible systematic changes in supernova brightness, such as might be caused by metal concentration of stars decreasing with distance/age.

So, if we just wait, LIGO will give an answer. Possibly, a third answer. If so, we will then have two problems, or maybe three: explaing why the Planck prediction is off, explaining why supernova brightness and/or redshift is off, and maybe even why LIGO is off.