It is recommended that you upgrade the router's Firmware whenever there is a new version.
Try to upgrade the router’s firmware to the latest one without keep setting.
Enter in your router's WebUI, go to System > Firmware:
Uncheck the box of keep all setting.
Select File as Source of the firmware image.
Click to browse your computer for a firmware image file.
Upload the firmware image to the router and attempts to verify its validity.
Click the Upgrade button to begin the update.
More information can be found here.
Target router FW: RUT9_R_00.07.01.4
Additionally, did you try to use different USB storage device?
Please let me know the result later.