Using a dataset of URLs marked as ’False’ by Science Feedback, an organization verifying the credibility of science-related viral information, we investigated the reach of groups and pages sharing misinformation on Facebook during 2019 and 2020, and Facebook’s actions to curb its spread. We found that, consistently with what the company publicly announced, Facebook removed large QAnon conspiracy accounts in August 2020, which were instrumental in spreading science misinformation. We also investigated Facebook’s 'repeat offenders' policy and found that only some accounts that repeatedly share misinformation display periods in which the popularity of their posts was temporarily reduced. Despite these measures, we have witnessed that most Facebook accounts spreading scientific misinformation have increased their reach at the beginning of the COVID-19 pandemic (March - June 2020), and that a drastic drop in their reach suddenly occurred around the 9th of June, 2020. Meanwhile the reach of a set of mainstream news accounts remained stable across the entire period. No public information was given by Facebook about this sudden decrease.