In the configuration file for systemd, you must not use environment variables.
E.g. this will lead to above error:
Environment=PATH=.:/appl/uc4/local/agent/smgr/bin:$PATH
You have to give the content of variable $PATH, not the variable name:
Environment="PATH=/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:.:/appl/uc4/local/agent/smgr/bin"