Out of curiosity had it been days or weeks since your norns has been connected to a wifi network?
There is a known bug in Supercollider where it will freak out and generate high CPU load when the system clock (on norns) is updated.
If you can get into maiden one thing to try is using the ;restart command in the “sc” repl - then reboot (sleep + power back on).
Another option is to select SYSTEM > RESET in the menu and see it f that cures the problem.