As I remembered, powerdvd supports auto switching screen refresh rate for playing movie discs, but not for any "video files" playback.
For HDR video playback, the screen refresh rate will increase to 60Hz anyway regardless of the original video frame rate.
What types of video you played?
Does your LCD support 24 Hz refresh rate exactly?
Here is an user community for experience sharing, but not cyberlink contact. If you think powerdvd has issues, you should contact cyberlink support, forum users cannot help you "fix" any issues by updating program codes for you.