Maintenance plan

I have 5 new SQL Server 2016 implementations at 5 different clients that exhibit the behavior below:

- Launch SSMS and connect to the SQL instance as 'sa' (or alternate sysadmin SQL login)

- Create a maintenance plan that can be as simple as performing a full backup of all databases

- Execute the maintenance plan

- Backup completes successfully

- SQL Server logs record  the following error:

Login failed for user 'sa'. Reason: Password did not match that for the login provided. [CLIENT: ] Error: 18456, Severity: 14, State: 8.

Followed by the logging of successful database backups.

- SQL Profiler trace indicates it is failing on the 'master' database.

- Creating an alternate SQL login with sysadmin role and creating maintenance plans using that new SQL login has the same results

This became an issue with one client who has 'enforce password policy' enabled on the 'sa' (or any other sysadmin) login with a domain password policy that locks out for 15 minutes after 3 failed logins.

What happens at that client is the scheduled maintenance plan starts, fails several times on the 'master' database then the backups fail because the 'sa' (or alternative sysadmin login) is now locked out.  So far the workaround is to disable 'enforce password policy' on the 'sa' (or alternate sysadmin) login.

Anyone have any ideas on how to resolve this?