Why does my Ender 5 Pro bed stops heating 10 °C below the set point
Searching the error message &quot;Heating Failed: Bed Printer Halted, Please Reset&quot; seems to indicate that the bed heater is timing out from not reaching temperature.

If you measure the voltage applied to the bed heater before the error message, does the voltage stay at Max.; i.e. 12V for a 12V bed heater?  Or, does the voltage stay constant?

If you raise the target bed temperature, does is still error out at stop at 50 °C?

Since you only indicate changing firmware, we would assume the bed heater is the same as when previously working.  Is this true?

Is the resistance of the bed heater a few ohms and not megaohms?