Why my statistics dropped by 50% in one day?

Hi all,
We’ve noticed that on 25th of November our visits statistics have dropped by 50%, and stayed on that level since then.

We are using on-premise instance, version 3.13.5. We can’t see any change in our software that could cause the situation.

The problem seems to be related with the Google Chrome browser. So maybe they had an update that influenced our logs? Did any of you experienced similar situation?

maybe the google core update?