A week and a half ago, we reported that Google had added an issue to their Google Search Console Data Anomalies page. The issue was specifically for image search results and caused lower than expected impression and click data.
Google has now updated this issue to include an end date and states that the reporting issue was fixed on October 22nd.
October 5–22
Logging anomalies occurred in image search results, resulting in a decline in impression and click data. This is especially noticeable on image driven sites. This was fixed on October 22.
Here is how it looks on the Data Anomalies page:
So if you have a site that gets a lot of image referrals, you should see accurate reporting after October 22nd. It isn’t clear if the older results have been corrected or if they will continue to show the lowered numbers.