Make sure you have full backups of your databases.
On the primary replica node, change the failover mode to manual
Refresh the databases and check if MSSQL reports any errors
Apply fix - CU0x service pack Perform an update for all databases until all fixes are uploaded.
After uploading patches and restarting MSSQL, check if the cluster is in good condition. P
erform an update for the Primary server.
After uploading all patches, check if the cluster is in good condition.
If there are no errors, change the switching mode from manual to automatic.