FlyingBear Reborn doesn't move + doesn't heat up correctly

FlyingBear Reborn printer with firmware Marlin v. 2.1.1.[ *this is public printer, but the person who serviced it is now absent, so I am trying to take over these functions and acquire the necessary knowledge for this. I still have little experience in this, so I apologize immediately if I did not specify something important ]It suddenly stopped working - the stepper motors do not work (when you try to submit the Homing command, the error "Homing failed" appears, the head does not move).I was told that the problem may be in the endstops - when checking them through Repetier-Host, they transmit their status correctly. The motor drivers were also replaced - this did not solve the problem either.There are also many errors with heating -the table does not always heat up, at a certain temperature (usually around 40 degrees C, but not necessarily) the heating stops, shows "Heating failed: " or "Heating failed: Bed", less often "Thermal runaway: " .The same thing happens with the heating of the extruder (it heats up to a certain temperature (~170 degrees C), after which it gives the error "Thermal runaway: E1" or "Heating failed: E1").I checked the power cable for the table heating element, it has 24 V as per the manual. The printer also measures the temperature of the table and the extruder correctly.This malfunction occurred without intervention in the printer, suddenly, after the completion of one of the prints.Maybe someone can suggest a plan of action to diagnose the problem? What can you do to understand more?I have connected the printer to the Repetier Host, but I still don't understand how it can be used for deep troubleshooting. I was expecting to get some kind of advanced error log with, but besides duplicating the errors I'm already seeing on the printer screen and checking endstops, I dont know what else I can do with it.I would be grateful for any answers