We are using mongodb-driver-core 4.2.3 & mongo db 4.2.
Authentication is done using Kerberos
When one of the MongoDB host was replaced in datacenter, it caused below error message
"Authentication Failed on Server XYZ" Code: 18 (mechanism GSSAPI)
We have 8 service instances and found this issue on 3 instances only.
Unfortunately, I won't be able to provide the full stack trace here.