Please check the mentioned steps for abnormal screen refresh rate:
1. Check what is the maximum screen refresh rate the device supports and whether matches to your requirement.
2. Check whether the app/game supports that much screen refresh rate.
3. If the device is not working on a high refresh rate but app/game supports, check with the app/game developer.
4. Check if you have enabled power saving or balanced mode in Game Space App.
We hope this will help you. Further, if the issue persists we recommend you to visit nearby Service Centre for a quick physical inspection.