Oracle allow remote sys access
SYS password is not necessarily the same for all the instances. Make sure remote_login_passwordfile is configured properly in the instances, and the password file exists for instance SID1 on the server in ORACLE_HOME/dbs/orapwSID1.
If you do not know the correct SYS password, you can recreate the password file, for example:
orapwd file=$ORACLE_HOME/dbs/orapwsid1 password= force=y
Format is important.