I tried it already but it is not helping.
The patch-client.jar file in our env is of 516 bytes. On all our instances it is of the same size. Where can I get a new file on Oracle website?
MOS note already addresses it and clearly states that "It should be 512 bytes," Maybe that's the issue but I m not sure.. This might change according to the installed version of Weblogic. That MOS note is for versions Version 9.0 to 10.3.6.
Don't you have a backup? If you have, can you check the patch-client.jar file from there?