Local Registry conf file (OLR) works fine, but reported corrupted and cannot be backed up
While shutting crs down in preparation of some maintenance work on the hosts it presumably crashed on node1 (there are 4 in the Exadata X5 cluster) but the RAC started later without any problem (I did not even notice the crash). The Cluster+Databases run flawlessly on all nodes.
But since then, the automatic backup of OLR file is failing on node1. This prevents doing any patch work of Grid or RDBMS because a backup is done implicitly when running opatch/opatchauto.
In short: RAC starts and runs fine on the problem host node1, but the corresponding OLR cannot be backed up. Look at this: