I found an odd issue today when trying to start up an PeopleSoft Environment Hub Agent. The environment uses PeopleTools 8.53 in a decoupled configuration. When running the StartAgent.sh file it was reporting an error that it could not find the binary psae to run for the validation/crawl. It was saying that it could not be found in null/bin. This seems weird because everything is setup correctly as far as environment variables go.
With a little digging around it turned out that the peopletools.properties file in the PS_CFG_HOME had an incorrect installation path. Once I changed that the crawl started working without an issue. The peopletools.properties file in the PS_HOME was correct, so just make sure you check all the homes.