A BAVID stands for ‘Bad Visitor ID’. The UI (every reporting product except Data Warehouse and Data Feeds) is susceptible to BAVIDs.
Starting in early to mid 2020, BAVIDs are being identified and removed from the UI
BAVID removal is done using the following logic:
If more than 1% of a report suite’s traffic is from the same visitor ID.
In some cases, if a suite is large, a bad visid can cause problems even though it does not reach the threshold of 1%. In such cases, the threshold may be adjusted down to 0.5% to removal of bad visids.
The percentage is best on a monthly basis–as Analytics data is stored in monthly grain files.
Common reason for a BAVID: populating Visitor IDs with a default visitor ID. Sometimes high bot traffic can also cause BAVIDs.
Comparing DW or a Data Feed to the UI is a good way to review situations involving BAVIDs.