Google has posted on the data anomalies page that the blocked resources report within the Google Search Console may have incorrect data being reported over a three-week period.
When pulling reports on dates between January 16, 2018, and February 22, 2018, Google said “users may see decreased counts of pages with blocked resources. This is due to a processing error on our side. Page counts should return to their correct levels within a few weeks.”
Here is a screen shot of this report. Please notice the vertical line that says “Note” which specifically documents this reporting issue:
