In that case it may have to do with the environment. The BigFix session is not running though a login shell and so may not have some environment variables populated that maybe your script or the binary depends upon.
You might try forcing it to run as a login shell (which sources the root account’s dot-files to build the environment) via
wait /bin/sh --login -c “/tmp/InstallSEA.sh > /tmp/seaout.txt 2>&1”
Also, check whether you have SELinux, fstab options, or any other security package that might block running executables from the /tmp path.