Risk Assessment will run and appear to have completed but it does not. Looking at the errors in the logs you will find the following error: AHD05535: An internal error occurred while updating risk level
Risk ranges are defined such that, it can take a maximum of 2500 by default.
The calculated risk for the survey above demonstrates the Risk Assessment going beyond the default risk range, hence setting the value as -1.
this can be rectified by either keeping the Risk Assessment range below the default maximum of 2500
update the risk range to a maximum level, maybe at 10000 and verify the issue.