Without more information for people to go with there is no way anyone can diagnose and respond to why you might be experiencing excessive processor core usage other than to suggest one leave the router alone and check back later to see if the processor usage changes or decreases. In the future, information like the following is helpful to provide context:
What router model?
What specific Asus-Merlin and or what Asus stock firmware?
How is the router configured?
What features and options are enabled on it?
Are you using features like; VPN, AiCloud, AiProtection, etc.?
Do you have a USB drive attached and are you accessing files on it (i.e. as a file server or media server)?
If running Asus-Merlin firmware, what specific addon scripts are you running?
Posting screen shots of the processor and RAM usage.
What specific troubleshooting steps have you tried including router reboot, power disconnection and reconnection, and firmware reset?
It helps to fill out the forum's profile signature line with router model, firmware, and any other configuration information to assist others.
