Thanks for the image and the details!
Sounds so interesting. Generally this should never happen of course becuse Hard Disk Sentinel (between the detection cycles) is just waiting, without performing any actions.
So (assuming that the detection frequency is the default 5 minutes), Hard Disk Sentinel is performing status detection only for a very short period (eg. 1 second or so) and for 4 minutes 59 seconds it is just waiting. There is nothing which can indicate/cause 100% CPU use.
One user reported similar - due to a failed Windows update and after the Windows update restarted and the system finished a reboot cycle, there were no further issues.
If you'll see next time, the best would be to (before terminating Hard Disk Sentinel) use Report menu -> Send test report to developer option - as it may give some ideas, thoughts.
Also if Hard Disk Sentinel closed, I recommend to please check the folder of the software and investigate which files modified just before terminating (eg. LOG.TXT) and send them in e-mail to info (at) hdsentinel (dot) com
This may give some ideas, thoughts about what happen on the actual system.