L&LD
Part of the Furniture
So its happening again
I see other users having similar issues
https://www.snbforums.com/threads/can-86u-handle-gigabit-speeds.56330/#post-485102
https://www.snbforums.com/threads/ac-88u-384-10_2-cpu-usage-discrepancies.56316/
I dont have spdmerling installed
If you uninstall all scripts and the issue persists, that would indicate its time for an M&M Config install again.
I can't remember if I've asked before, but when was the last time you did a full reset to factory defaults on the router?