SO I have built new CoreXY printer. It prints great, but I have a problem. Heated bed is having hard time heating up. Though on Marlin 1.1.9 on MKS Gen_L I have no problem. I have set Bed max power to 255 and enabled PID and autotuned. But whenever I turn on heating the diod in board not light up all the ti, but blinks indicating not full duty cycle and voltage at terminals are fluctuating from 6 to 7.5 volts and never goes to 12. Is there a problem with heated bed when using Marlin 2.0 on SKR 1.3?

Noticed that during PID autotune diode not blinking. But when I set temp on BIGTREETECH TFT28 it blinks