Updating the same User resource in multiple concurrent requests may cause data inconsistency. This may result in that searches using multiple Segments will not find your User resource even if it should belong to all the specified Segments.
Possible Causes
Updating the same User resource (e.g. adding or removing it to/from Segments) in multiple requests concurrently.
Possible Solutions
Change implementation so that if you need to add a User to multiple Segments at once you wait for each request to complete before trying the next one.
For past errors, just read the affected User resource by using the
Read User API
this will fix the data inconsistency.