Google has acknowledged that there was a bug within the performance reports in Google Search Console that ended up impacting reporting around Google Discover traffic.
Between the 8th and 13 of December, Google Discover impressions and clicks may have been reported inaccurately. Google wrote, “Because of an internal issue, you will see a data drop in the Performance report for Discover during this period.”
On Monday, Google said, “This issue has been fixed.” The data seems to be lost, but going forward, you should not see this issue after the 13th.
This bug didn’t affect the performance or real traffic of your web site. This was just a reporting glitch. Google wrote, “Please note that this does not reflect any user-facing changes for your site, only the data reporting in Search Console.”