How I can make all SQL cluster nodes on the same version level

We have SQL 2005 cluster (2 nodes). One of the node on service pack 2 and the other node without service pack. This cluster was configured long time ago by a vendor. I think that the seconed node was added after they have applied sp2 to the first node.
The issue is whenever the failover happened, most of the jobs failed because incompatiltiy. I have tried to apply service pack 2 again it shows errors and rolling back all the actions. I am thinking in 2 action plans:

1- either I go to apply service pack 3 to the cluster
2- remove the node (which without service pack) and re-added again

Please advise

Kind Regards
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Your second option should be done first just in case you applied a hotfix that is not included in the SP3.
Get the nodes to the same sp level.

Once they are on the same SP level you can rejoin the node to the cluster and bring them up-to-date with sp3.

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Microsoft SQL Server 2005

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