Tienes la tarjeta SD puesta y te funciona bien, verdad?
La pausa es normal que te la haga bien ya que, aún que se parezcan, para Marlin son operaciones totalmente diferentes.
Antes de quitarle la corriente, mándale un M413 y te responderá con el estado del "power loss recovery". Asegúrate que este ON.
La verdad que Marlin2 no lo conozco en profundidad, pero siempre que surge el tema, invito a cualquiera que me diga 1 función que no esté en Marlin 1.1.9 y pueda usarse con electronicas de 8bit. De momento 0.
Que yo sepa todo el desarrollo de Marlin2 se centra en dar compatibilidad al mayor número de procesadores de 32bit, y todos los problemas derivados de esto.
Marlin1.1.9 tiene dos protecciones que paran la impresora ante el fallo de ambos termistores. Están al principio de Configuration_adv.h
Cita:/**
* Thermal Protection provides additional protection to your printer from damage
* and fire. Marlin always includes safe min and max temperature ranges which
* protect against a broken or disconnected thermistor wire.
*
* The issue: If a thermistor falls out, it will report the much lower
* temperature of the air in the room, and the the firmware will keep
* the heater on.
*
* The solution: Once the temperature reaches the target, start observing.
* If the temperature stays too far below the target (hysteresis) for too
* long (period), the firmware will halt the machine as a safety precaution.
*
* If you get false positives for "Thermal Runaway", increase
* THERMAL_PROTECTION_HYSTERESIS and/or THERMAL_PROTECTION_PERIOD
*/
#if ENABLED(THERMAL_PROTECTION_HOTENDS)
#define THERMAL_PROTECTION_PERIOD 40 // Seconds
#define THERMAL_PROTECTION_HYSTERESIS 4 // Degrees Celsius
/**
* Whenever an M104, M109, or M303 increases the target temperature, the
* firmware will wait for the WATCH_TEMP_PERIOD to expire. If the temperature
* hasn't increased by WATCH_TEMP_INCREASE degrees, the machine is halted and
* requires a hard reset. This test restarts with any M104/M109/M303, but only
* if the current temperature is far enough below the target for a reliable
* test.
*
* If you get false positives for "Heating failed", increase WATCH_TEMP_PERIOD
* and/or decrease WATCH_TEMP_INCREASE. WATCH_TEMP_INCREASE should not be set
* below 2.
*/
#define WATCH_TEMP_PERIOD 20 // Seconds
#define WATCH_TEMP_INCREASE 2 // Degrees Celsius
#endif
/**
* Thermal Protection parameters for the bed are just as above for hotends.
*/
#if ENABLED(THERMAL_PROTECTION_BED)
#define THERMAL_PROTECTION_BED_PERIOD 20 // Seconds
#define THERMAL_PROTECTION_BED_HYSTERESIS 2 // Degrees Celsius
/**
* As described above, except for the bed (M140/M190/M303).
*/
#define WATCH_BED_TEMP_PERIOD 60 // Seconds
#define WATCH_BED_TEMP_INCREASE 2 // Degrees Celsius
#endif
Incluso tiene otra opción para poner un segundo termistor para hacer una medición redundante.