BranoI hate VogonsPremium,MVMReviews:
Direct logs to remote log server or if you don't have one you can direct logs to USB stick that you plug into the router.
If the unit acts up (happens from time to time) my typical remedy is
- reflash the firmware
- reset to factory defaults after flash
- reconfigure the router manually from scratch (do not restore old backup)
...I've seen USG routers behaving weirdly after 2.20 to 3.00 upgrade, starting with vanilla 3.00 config resolved the issues