Most likely incorrect/invalid environment variables, or incorrect version of Opatch being used. Have all of the steps in the pre-install section of the README of the patch been completed without error ? Search for the error in MOS and you will get a few hits
Check the following MOS: Opatch Failed With Error Code 1 : java.lang.UnsupportedClassVersionError oracle/opatch/OPatch (Unsupported major.minor version 49.0) (Doc ID 1352579.1)
-Chiranjeevi M A
Opatch issues :
- Environment issues (it's all not that complicated, but I see ppl do that wrong on may occasions)
- Inventory issues : not pointing to the one you are patching, permissions issues, ...
- Version : although a lot of patches are around, a lot of documentation, I don't often see it fail because of versioning (but then, I always upgrade opatch)