Huge change in visits after update to 3.5.1

Hi,

Since we updated from 2.17 to 3.5.1, we’ve seen a big change in visits and unique visitors counts which does not reflect on server load or sales.

The count went from about 40k visits / day (which was consistent with what we had on GA) to about 65k. Page views are relatively stable though.

No other changes were made in API calls or JS tracking tag.

Is this due to a change on how Matomo counts visits ?