As a thought, could you ask your domain controller manager to check their logs if the account got locked at the time the job failed?
Is it always the "backup" job that fails? Your second post (the one with the errors) shows a transaction log backup failure. Or is it intermittent as to what fails?
Do the logs on the remote server (where you are storing the backups) show anything interesting?
And another thought - are you using UNC paths for the folder share or drive letters? If you are using drive letters, I would try switching to UNC paths as it could be something related to that.
And my last thought - are the jobs that fail always writing to a remote server or do they fail when writing locally as well at times?
The above is all just my opinion on what you should do.
As with all advice you find on a random internet forum - you shouldn't blindly follow it. Always test on a test server to see if there is negative side effects before making changes to live!
I recommend you NEVER run "random code" you found online on any system you care about UNLESS you understand and can verify the code OR you don't care if the code trashes your system.