Maybe in your Firmware is PID active even for your Heated Bed, try tu run the Nozzle and the Bed PID M303 C10 E0 S210 U1 // Hotend - 10 runs to 210 degree M303 C10 E-1 S60 U1 // Bed - 10 runs to 60 degree use some software like for sample Pronterface, to see all the responses from the printer, after it states that the PID-Autotune is finished, save with an M500 Kind Regards