Did u setup the user ssh Equivalence in both node 1 and node 2? --> very important requirement
And also let me know , are you trying to upgrade non rac DB1 from to 188.8.131.52 home?
Oracle Support said to perform the upgrade manually. DBUA is confused because we have grid infrastructure installed on the node to be upgraded, but the DB to be upgraded on the node is non-rac. I was able to complete the upgrade manually. I'll ask support to create a bug for this.