Klipper sometimes doesn't connect to mcu error:-32601

Basic Information:

Printer Model: Flsun super racer
MCU / Printerboard: Mks robin nano v3.1
klippy.log (473.8 KB)
moonraker.log (859.9 KB)

Describe your issue:

I have a super racer klipperized, it works all perfectly via usb, but when i connect raspberry pi 3a+ to the mcu via uart, klipper stuck to “status:startup” on mainsail and “unknown” on fluidd, i’ve noticed an error in moonraker.log(code:-32601) but i don’t know what it mean. I have always to restart the printer 2 o 3 times to make it work. I want to connect it via uart to put raspberry inside the case of the printer.

From the log it seems that even the USB connection is unstable.
Refer to Got EOF when reading from device and Timeout with MCU / Lost communication with MCU for potential reasons.