I’m actually out sick today and haven’t logged in to my lab, but I’d note that at least on Windows, the output redirection is a function of the shell (cmd.exe) not the individual application that’s executing. I suspect it’s the same case on Linux - the “&>” would be something interpreted by /bin/bash, not by /bin/tar.
Also, if you’re backgrounding the application, I’m not sure I’d actually expect the output to end up in the /tmp/error.txt if there were a failure.
I’d try using the shell to run it instead, something like
run /bin/sh --login -c "tar -cvzpf /tmp/bkp5.tar.gz --exclude=/root/Test/sample1.log /root/Test 2> /tmp/error.txt"