On database servers using ASM as storage, DBCA (the tool to create a database), DBUA (tool to upgrade), "srvctl start" (to start database or instance) implicitly change DB_HOME/bin/oracle's group ownership to that of GRID if they differ, even though the DBA team do not wish to separate the GRID and DB roles. This unconditional change takes no account that there may be a running instance; changing the binary while an instance is up and running makes the instance unusable. The correct behavior should be that of OPatch, i.e. abort and give a warning if an instance is running. There should also be an option for these tools to bypass the call to setasmgid (or setasmgidwrap).
More details are at http://yong321.freeshell.org/oranotes/OracleBinaryGroupOwnership.txt