Hi,
Being logged in to the server and able to connect from OME will be 2 different things. There are occasions when after system update, the system becomes unreachable from a remote location. OMe needs to connect to the target server using OMSA installed on the target server if you are doing a system update via OMSA method.
It is not normal for tasks to fail when they have already applied but can happen depending on various network features and which DUP you are trying to update. Now since you have mentioned you normally apply all packages it is possible that the targey system goes to unreachable mode for sometime. I would suggest you to try by applying one of the DUPs (packages) to target server and let us know if it still fails.
Thanks
Pupul