I recently came accross a new (to me) error when trying to upgrade Grid Infrastructure on my lab, a 2-node 18.6 RAC cluster. To upgrade Grid Infrastructure directly to 19c with the latest Release Update 19.4, I downloaded the 19.3 base release and tried to apply RU 19.4 before launching the upgrade :

# /u01/app/19_4_0_0/grid/gridSetup.sh -silent -applyRU /staging/path/29708769

(Please refer to Doc ID 1410202.1 for the full explanation.)

Unfortunately, I had my head in the clouds (pun intended), and the node on which the patch was running encountered a problem and the session got killed.