SQL 2012 :: Cannot Drop Orphaned Account

All is happened when a server crashed some weeks ago and it was removed from my network. After that, under my SQL Server 2012 I get an orphaned account which cannot be removed. This account is a computer account related to an old SCOM installation.

If I try to execute the command DROP USER [NETWORKSERVERNAME$] I get the following error message:

The database principal has granted or denied permissions to objects in the database and cannot be dropped. Msg 15284, Level 16, State 1, Line 1

The database principal has granted or denied permissions to objects in the database and cannot be dropped.But if I run the following command to know all permission granted to the account, I get an empty result:

select * from sys.database_permissions where grantee_principal_id = user_id ('NetworkSERVERNAME$');

Furthermore, following the instructions provided by the official KB for troubleshooting orphaned users, I get another error [URL].

sp_change_users_login 'update_one', 'NetworkSERVERNAME$', 'NetworkSERVERNAME$'
Msg 15291, Level 16, State 1, Procedure sp_change_users_login, Line 114
Terminating this procedure. The User name 'NetworkSERVERNAME$' is absent or invalid.

The only thing I can retrieve is 15 permissions that this account granted to another account in the past:

select *
from sys.database_permissions
where grantor_principal_id = user_id ('NetworkSERVERNAME$'
--
class class_desc major_id minor_id grantee_principal_id grantor_principal_id type permission_name state state_desc
17 SERVICE 65538 0 5 19 SN SEND G GRANT
And more 14 rows…

resolve my issue and safe delete the account SERVERNAME$? I need this because I have to reinstall SCOM with the same computer name on another server, but installation fails due to this behavior.