Remove your USB-connected disk, restart the device, ram usage drops to around 60%. If you use it without a flash disk attached to USB, you will use the device stable with around 60% ram usage. If you do not do anything on the usb with the usb disk inserted, the ram usage will appear as 60%. The slightest operation (copying, writing, moving, etc.) on the usb disk will increase your ram usage up to 97% and it will stay stuck in that state. Asus was unable to fix this situation. Tp link routers do not have such a problem. I am using Asus GT-AX6000. I also own the Tp Link Archer C4000 router.