Deleted DNS record keep coming back

Hi,

I had a Windows Server 2008 R2 Domain Controller that was successfully demoted.
Now I want to reinstall the server with Windows Server 2012 R2, using the same hostname.

When the server was a DC running Server 2008 R2 the hostname of the server was in lower case letters.
Since a few years we have switched to using upper case letters for our servers hostnames.

Before I reinstalled the server with Server 2012 R2 I first deleted the servers entry in the Active Directory-Integrated DNS zone and also deleted the AD computer account.
Then I waited for replication to occur between all remaining DCs.

Once the DNS record and computer account was nowhere to be found on any DC I went into ADSI Edit and deleted the record at:

DC=hostnameinlovercase,DC=domain.tld,CN=MicrosoftDNS,DC=DomainDnsZones,DC=domain,DC=tld

Again, waited for replication to occur. Once the record was deleted on all DCs I reinstalled the server using the hostname in uppercase.

But when the installation was completed the entry in DNS got added with lowercase letters.

I then reinstalled the server using a hostname I know never have been used in our domain. That name is added with uppercase letters.

I get the feeling the original hostname is still stored in the AD somewhere. Could you guys help me figure out what is going on and how I can make sure the hostname is registered with uppercase letters?

Regards Erik