On August 1st, we reported there was a bug with the Google Search Console data in the Search Analytics report. In short, Search Analytics would mislabel the mobile and tablet search traffic as being desktop traffic between the dates of July 29th and August 1st.
Well, it now looks like Google extended that date through August 5th.
Google updated their data anomalies page to write:
July 29 – Aug 5, 2016All traffic in Search Analytics was erroneously labeled as "Desktop" traffic in the "Devices" grouping category. This mislabeling was corrected on Aug 5. We hope to be able to retroactively correct the data for this period.
I checked myself and it does seem like the numbers went back to normal for me on August 4th but there obviously is a reason Google posted August 5th.
Here is a screen shot:
Forum discussion at Google+.