How did you target your SEP installations? Do you have a compliance rule created? Are you evaulating compliance in your policy using that rule?
I bet that your policy is making the computer reboot after installation is complete. However, the SEP installation is running (remediating) over and over but it's finishing without changing anything because the software is already installed.
Either you should target a shrinking filter that's based on inventory or you'll need to create a compliance rule and use that for detection. Once the compliance rule is built and associated with your policy the remediation will not happen unless the targeted computer no longer is compliant.
EDIT: I kept saying "compliance rule" but I meant "detection rule". You would create this by opening the software release for your SEP deployment and building it there. The best one to use (in most cases) is the MSI Product Code